Wis is a good idea. It's been so useless for now that I completely forgot about it. Since spell resist would be useful to both melee and casters, you'd have Melee needing STR and DEX with WIS and CON as useful, and casters using INT and Essence with WIS and CON as useful.
I think Wisdom is very useful, because Wisdom is Essence as soon you leave the character creation and if you play Empire you get your maximum mana every turn (is that a bug?), which makes Wisdom very powerful.
I have started a new game (Empire this time, small map, 4 opponents, challenging) and my favorite spell is Melt Touch, because it inflicts a base damage of Intelligence x 2 points at a range of 2. With Intelligence 17 and 2 shards the spell inflicts 0 - 102 points of damage for 2 mana and i can cast this spell 3 times per turn (mounted spell casters are nice).
Most stats should be rebalanced:
CON: Base Hit Points and CON / 5 Hit Points per level beyond the first
STR: Is balanced
DEX: Is balanced
INT: As STR, all spells should have a base damage of 5-15 and every shard should increase the INT by 5 for that type of spell
WIS: Base Mana and WIS / 5 Mana Regeneration per turn
CHA: Should change the gildar cost of all units (100 % +/- 5 % per point CHA below or above 10)