Such good feedback, thanks.  But lets compare everything.

Contagion is a rank 2 spell (requires 2 air and 2 death) so it is available to 3rd level casters, starting sovereigns could have it.  It costs 18 mana and takes 1 action to cast.  It does 3 poison damage (+1 per death shard) to every enemy in battle every turn for 10 turns.

Fireball is a rank 3 spell, you have to be at least 5th level to know it.  It costs 30 mana to cast and takes 4 actions to cast (3 in your build).  It does 4 fire damage + 4 per fire shard (6 + 3 in your build) and has Overkill (damage is multiplied by the members of a group).  It does damage to all units in 1 radius.

Dirge of Ceresa is a Rank 4 death spell, a caster must be at least 7th level to be able to cast it.  It costs 24 mana and takes 2 actions to cast.  It is a special spell (only available to players that have selected the Death Worship faction ability). It does 6 (+3 per death shard) poison damage with Overkill and then 3 (+1 per death shard) poison damage per turn for 10 turns.

Based on the spells rank these spells are not supposed to be even.  And their relative strength is in line with the their ranks (contagion then fireball then the dirge).  So far, so good.

But I do agree that contagion is still a little to weak and the Dirge is a little to good, so Im going to make the following tweaks.

Contagion takes an additional action to cast and goes to 3 (+3 per death shard) poison damage per turn.

Fireball has already been modified in my build as you may have noted above (an additional action to cast, less base damage, more damage from fire shards).

Dirge of Ceresa becomes resistable and has its mana cost increased from 24 to 36.

As a follow-up, first I will say thank you for looking at this balance issue.  My next comment is that there are quite a few spells such as Contagion that might never been seen by anyone unless they read the manual carefully and then deliberately build to access them.  I didn't even know it existed until I went through the entire Hiergamon (spelling?), wrote down each spell that required multiple types to access and then made an effort to try them out.  None of the premade Empire Sovereigns even has the Air school at all, much less Air + Death, so the only way anyone could find this spell was to do what I did, or to recruit a hero who happened to have that combination.

BTW, what is your definition of an 'additional action'?  With your example of Fireball you state that it now takes four actions to cast (three in my build)?  At the moment my most common method of casting Fireball is through the Impulsive trait, which is basically an automatic 'I go first and nuke you into oblivion' option, since if your initiative is good you'll get two actions back to back and instantly cast Fireball or whatever else it is you need to get off.  As far as I can tell Fireball only takes two actions right now...

Bonus note - Stinking Mud is amazingly strong if you build a force around it.  I think it's balanced, and there is only one Sovereign which can access it straight up (Kul-Al-Kulan), but WOW is it good if you have a bunch of archers.  Stinking Mud, follow up with Mass Curse to lower their defenses, then let your archers do their thing.  More Stinking Mud or other debuffs such as umm the mass slow (H. Wail?  can't remember) as appropriate.

- Manii Names

Yes.  What is the point of spending research points getting all the way to high-tech, advanced, 9 person armies when a spell from pretty much the start of the game does extra damage precisely *because* there are more units AND to make it even worse there is no resistance to damage spells unless you have resistance to the element itself?  Either fireball and blizzard need to be reduced in base damage, or overkill needs to be removed from everything but monsters that can never be on a player's side.

The thing is, Dirge's extra power is next-to-useless. Fireball is already so efficient that Dirge basically does the same thing: it kills every trained unit.

I don't understand the rationale behind a fireball so powerful it kills the units outright for a moderately experienced spellcaster. If it reduced the number of soldiers in a unit by 50%, it would already be very good. Unless there are many planed ways for extra unit HP, I don't see how this is supposed to work.

Sure, the increase in casting time will tone things down a bit, but it doesn't remove the problem that it makes spells of higher level (such as Dirge) irrelevant, and doesn't scale with higher level of mage power/fire shards since 1 shard and evoker I is already enough to remove all trained units, even of level 2.

Although that would not be possible currently, as I think every spell you cast that requires casting time replaces the one that has come before.  I don't think there is currently a possibility to "start casting a spell with multiple casters to prevent one spell from being countered".  Basically, even with the extra turns required, Fireball and Blizzard are broken with current game mechanics.  You shouldn't get extra damage from an early game spell with no extra research on someone who has spent most of their research teching up to 9-man groups.

No.  Only one spell per side can be charged up currently in tactical combat.  If you cast another spell, either the current spell is wasted or the earlier spells are wasted (I think it is the latter).  So unless they change that mechanic, Fireball and Blizzard are broken, or if a Counterspell is available, totally useless.

Maybe, it has been mentioned, but not necessarily on a bug report of its own.  You'll have to ask Derek whether it's intentional.

I just tried this with the current internal build (2 of my guys casting fireball at the same time) and it worked fine.  We have fixed some bugs with the way casting times worked that may have resolved this.  But multiple units are supposed to be able to cast spells with casting times at the same time and it appears to be working correctly in my testing (with the internal build).

Exactly! The spells shouldn't be balanced to be just about equal. There should be outright stronger and weaker choices. Fire should have the most powerful direct damage spells. Sure a Death spell might take longer to do the same amount of damage but thats the flavor (advantage/disadvantage) of the two elements. Death might have stronger debuffs and stuff that will make it more useful in that regard. Fireball in no way makes Dirge or contagion obselete. For one Fireball should be somewhat better and for two there is no garuantee a mage will have access to both spells . . . if you're going to make everything the same why even bother with the different elements. Do you remember how the spells in the initial release of WoM was? Each school was basically a clone of the other with different color effects. It was boring . . .

It is possible that regular units are getting a boost to hp. We don't have the new build so all we can do is speculate. Rather frustrating I know, but that is why I have so many mod projects to work on. If WoM taught me nothing else, it was patience. 

Haha, I know. The reason I just found out about the casting times bug is because I have never needed to use more than one Fireball per battle. 

Not that your points are any less valid/interesting, but Tasunke... do you have the beta? 

Each soldier in a unit does in fact have his own hp. 

AoE currently gives damage per unit and then subtracts that number from the total health AFAIK. Your idea would actually have the same effect 90% of the time. Making AoE weaker in your way only works until someone gets 2 Fireshards. Then the other players are totally screwed because they can't kill with Fireballs. 

The additional action is a great change to fireball and hopefully to blizzard, too, but decreasing the base damage and increasing the shard based damage makes the spell less useful if the player has bad luck with the shards on the map and more powerful if the player is lucky with the shards on the map.

I think FE needs LESS 1^n events, but currently the luck is very important, because it gives the player shards of the required type, champions of the required type, monsters of the required level, powerful loot and powerful talents.