Excellent points and i guess i kinda agree.  What motivated me to post was i had 2 games where i had explored the entire map and some how missed them, forcing me to take my scout across the whole map again.  Fully equipping with +1/+2 sight crafts helps a bunch but it is still a long hike to re-explore med. and up maps.   Also, you may find them early and by the time your ready to take then on you forget the general area or they moved on   

Would a skill after the skill with +1 to cast tactical spell be an option placed late in the skill tree be a solution.

I mean by the time you reach the later parts of the game you have probably also gained a lot of the skills in the sovereigns skill tree. Hence skill for pointing in the right direction of lieutenants would not be overpowered/misuse.  

The skill could have different names such as Evil compass for the Tinker, seek evil (displaying points on the map with signifcant monster with a combat rating of 50+ until 'end turn') for the Priest, Jealous sovereign for Tyrant, Compass of Power for Wizard etc. 

Now that would be a good way to do it.  It would be late game, presumably most/all of the map has been explored, and being a late skill you might even need to XP mining to get it.

Enrage the SK enough he should send the lieutenants after you.   Either that, or create a blast gate spell for a lot of mana that allows you to get around the lieutenant finding if you're in mop-up phase.

I feel your pain.  And enraging the SK did not help.

My method- equip scout with 3 +2 sight and 3 +1 moves and you can scour the whole map quickly

I ended up running around with two scouts and found one army. I never found the second but the gates opened anyway witha single key - odd

Anyway it made for a very frustrating and boring end game

The worst time I had finding a lieutenant was when he was hiding on an island. I was tracking back and forth across the map constantly trying to find any clue of him.

Eventually noticed a small patch of undiscovered land and had just gotten the summon boat spell so I went to check it out. Lo and behold...the big bugger was taking a vacation on an island...gah!

I just had the opposite problem: Around turn 40, right after I founded Avalan (2nd city), Vetrar + 2 brutes came looking for me (or the shard adjacent to my 1st city).  My L6 Tandis + 2 dwarves + 2 pikemen were estimated to have "crushing defeat", but Tandis wasting 1 turn on Inspire (+15% dodge) actually made Vetrar miss almost half his (many, many) swings.  (Vetrar must have Initiative 30 or so!!)  Halfway through, it occurred to me: oh duh I might as well cast Graveseal on him for yuks and more testing -- and then he killed the 4 peons first, and Tandis won   Vetrar can one-shot for 120+ hp damage, ugh.  I unlocked the achievement for beating a "crushing defeat" odds

Seriously tho ... it's a tad unfair to have Vetrar attack my 1st city when I'm still having trouble with Medium huts.  Saved me the bother, tho.  Tandis alone is actually faster by +1/turn, neener -- I might keep him that way and just solo a bunch of strongholds.

I love the lieutenant on an island.  I've started on an island before, so I think the lieutenant groups can never paradrop there (because they start on the map).  The sadistic DM can just paradrop monster rings onto your island, tho.

The DM should allow lieutenants + SK's strategic map magic to slowly construct a mole (spit of land connecting the mainland to an island city), e.g. by tearing down nearby forest hexes.  Alexander the Whodat did this to the (formerly-a-)fortress city of Tyr, and after a few weeks their citizens stopped laughing when it became clear to both sides that it was working, and would inevitably succeed.  (Today the "mainland" simply includes all of what used to be Tyr, and Alexander's land spit has had numerous roadways constructed upon it, including the modern highway.)  After that, he was Alexander the Not Bad ...