The upside to a shared casting pool is that aside from fixing more casters = more mana regen, it lets you have big spells. You can't have 100 mana spells right now, because it's effectively impossible to get any caster to that point.
...
Don't you just hate it when when one says something and some jerk comes along and...?
That's from an 8th level progeny, in a 1.06 game, turn 454. Wife has 85 essence, other kids have 88, 88, and 99 essence. Pops only has 72 (from imbuing 9 champs including the wife - he'd have, what... 27x3.55=95.85+72=167 if he hadn't imbued anyone).
That said, I agree with your point. The above essence is due primarily to the apparently cumulative 50% bonus from a number of Temples of Essence, which seems overpowered and I'm not convinced is as intended.
EDITED TO ADD:
It occurred to me that some may think the above is an artifact from 1.06 and not representative of 1.07. In my 1.07 game on turn 176 my sov has 70.2 essence (19.5 base and 260% bonus = 70.2). He imbued 3 champs so far so add in 9x3.6=32.4 32.4+70.2=102.6 total had he not imbued. And the game is barely begun, mid-early game stage, with only 6 cities (one crap and will be soon deleted) and no shards.
