Some of these may have been mentioned, but I figured I would put in my 2 cents.

I personally am not a big fan of having all monsters in the world be whatever level the player is. Currently it is no big deal to have a few champions and/or units run around and kill the monsters. I would personally like a variety of monsters of varying levels of skill. 

Monster lairs that are in areas that make sense. Wolves in forest tiles, perhaps giants in hills, other creatures in caves, etc.

The lair would be guarded by a few of that type. So a couple of giants, a pack of wolves, a lair of spiders, etc.

They would spawn wandering monsters based on their sizs/type. So spiders would spawn very frequently, giants perhaps once every 100 turns or so. These would start weak, but get stronger and wander about looking for suitable lair locations of their own. So you need to deal with them as they are going to be competing for living space with you.

I have no problem with certain map locations being so tough, you can't do anything to get there for a time. A "Valley of Doom", or "Pit of Despair" < insert "Princess Bride" quotes here> Once you do, there could be a really cool goodie for your trouble.

 Fertile lands, groves, gems, ore, shards, etc are just lying around with nothing around trying to use it. I feel it would be more interesting if it were almost a quest in itself to get one by having to fight off animals that are either living there or prey on animals that would be eating the crops. Have shards protected by magical creatures that would also draw power from the shard for their existence.

Either that or perhaps have shards hidden except for certain side effects in the area. You can only find the exact location by using a channeler.

Thanks for reading