I'm sure I'm the millionth player to throw out an idea, but honestly the only real problem I see with Summoner right now is target switching. So, I feel like the answer is simple and obvious...
Let's just remove the cd from tri-disaster and remove Miasma and Bio as separate skills entirely, once tri-disaster is available. If we have to nerf ruination to make up for it having more uptime then whatever, but I personally don't think the buff would be completely unwarranted.
If we need those dots up to do put out our real damage then they shouldn't be time consuming or prohibitive to apply.