Here's my interim house rules for evocation:
1
By agreement, the PCs should keep their base (including foci) evocation power + control totals at (refresh +4) or lower.
So, for example, in a submerged game, the limit would be a total of 14 (power + control).
This prevents the more extreme ends of evocation min-maxing.
2
Allow counterspells to be used defensively, like evocation blocks.
Advantage:
the counterspell is a power vs power contest, so if your opponent is using low power, high control attacks, you are better of using a counterspell against the attack, rather than a block.
Disadvantage:
defensive counterspells are not persistent, like evocation blocks are.
This rule is there to shut down jokers who make their evocation attacks very heavily control biased. For example, a submerged character under rule 1 can still have a power 4, control 10 base attack. But as you'd only need a power 4 counterspell to shut them down, that route isn't as attractive as it could be.
This also limits wizards to blocks of (refresh +4)/2 (example: power 7 at refresh 10), which will hopefully keep their defenses powerful but hittable too.
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This still lets wizards throw around very powerful attacks, but hopefully keeps them from getting too out of hand.
Another rule house rule I'm considering is to limit refinement to +1 power or control instead of +2. You can go 'unbalance' by getting +2 via foci for the same point cost, but this makes better foci vs straight up power or control more of a trade off.