I think the big issue is that summoner needs a consistent increase in MP regen and not something that is proc'd or RNG based. Because you are guaranteed to run out of MP; and not being able to DPS because of bad luck is bad indeed.

Easiest fix I think is simply an enhanced energy drain for summoner only with an increased potency and mp refresh in addition to making ruin cost less mana. Its more in line with the way SE commonly buffs thing and wouldn't buff SCH in anyway.