Neurotoxic Breath: Weaken: Envenom and the Alkaloid.
I think these are the most used skills from poison, until you get the ranged hold.
Neurotoxic Breath does more than slows them down, it affects the attack speed too.
Currently i have only two slotted this, but there is time to add more.
I've had bosses just stand there for around 3 seconds doing nothing.
Acc/Slow
Weaken;
this attacks every action the target can do and makes them less effective, or makes them miss more.
4 Slotted currently: 2 acc / 2 To Hit Debuff
Envenom: targets the defense, more damage/hits from you.
4 Slotted currently: 1 acc / 3 defense (still hits almost everytime).
Alkaloid: 6 slotted: 3 end , 3 heal. for me, that works.
I dont know about undead so, maybe someone fill that side, but with poison keep the debuffs on the hard targets and use heals when needed. Yes your going to be busy sometimes 
. I would start with malicious and see how it goes, then when you really feel like it jump to ruthless.
In my opionion, some ruthless missions are simple while others make you sweat. So i couldn't say that they are "easy", just had an tough fight against Archon Galaxy and friends (multiple minions). I escaped certain defeat with 5 hp left, think about it 
. But thats the hole point, i do them because of the added challenge.
I'm only 12 at the moment but I've taken Zombies, Enchant and Grave Knight from Necromancy and Alkaloid (have to), Envenom, Weaken and Neurotoxic Breath from Poison. So far it's working out really well and now I'm getting DOs it's suddenly a lot easier. I also took TP Friend so I'm on track for a travel power at 14.
Avoid the blasts since you'll be too busy healing and debuffing to use them much and their damage won't do much at all compared to your minions. I'm fairly sure Life Drain sucks horribly so I'm avoiding that.
Also make yourself a macro so you can easily tell your pets to go to a location. This is very important for getting your zombies into melee range.
I played on the middle difficulty level up until this point but since I hit 12 and got my first Knight and some DOs even that's become fairly trivial so I'm probably going to increase it.
can any 1 help me plz with a good build. as i see other MMs soloing 2 lvls higher than them yet i find it hard to solo baddies my lvl.