I've played COH on and off for a long time, I've never really played MM until recently
I found time, as it is with a corruptor is very good, the extra recharge you can afford yourself opens up many builds like perma serum for mercs, the recharge also helps your team a lot.
Currently I am playing a Merc/Elec affinity and I'm throughly enjoying it, it feels like I can keep the team up well and I'm giving lots of absorbs, recharge times, damage, to hit bonuses. I am close to getting perma serum which is big but not there yet.
I've yet to play Dark, everyone says it's amazing and I've seen it in teams - it is good! Necro/Dark should let you handle most things.
Wish that Minions were the same level as the hero themselves, only the final one is the same level as you, the other 2 summons are 1-2 levels below meaning if you do hit +4 content it will be a little tough to 'feel useful', perhaps in the future the HC team might look at MM's and buff pet levels 🙂