I am a thugs/poison lvl 50.
I love poison. It's the best single target debuffing power in-game (or so I hear).
And when you top the weaken/envenom combo up with neurotoxic breath and Noxic Gas a lot of enemies will just try and run away instead of feebly attempting to hit your pets. (not that with the -speed they get far, or that with the -res they stand much chance against your paralytic poison)
Your pets should be enough to handle normal enemies, and though posion doesn't have the nice aoe heals some other sets have, the paln is that the big opponents wont really do all that much damage to require aoe heals anymore.
I have a Necro/Poison MM...which is currently at lvl 30. I personally would stick with Poison (if I were you), especially as I have just started using Paralytic Poison. This single foe hold power is great on lieuts, as can normally defeat them before the hold wears off. Alkaloid is a pretty good heal power too, maybe one of my most used ones...with 3 Tier 1 zombies to try and keep alive.
I prefer Poison 100% compared to FF (only 2 secondaries I've used above lvl 25) as the single target debuffs are great. Envenom and weaken, in conjunction with Neurotoxic Breath... almost reduce your dmg received to zero. I can't remember the last time my MM died... Zombies yes, but never me...!
Main 50 & Badger Nine Claws Claws/Regen/Body
Other 50's Ph10x Brute Unjust Law Tanker Samantha Urai Scrapper Codename 1250 Scrapper
Cepheus Defender Nilus Scrapper Electro Field Blaster S.PONGE Tanker
just had a great group, going to stick with the poison, the debuffs are shining in groups (slotted some acc and rech) and I noticed that single heal is realy nice now for saving someone if the Twilight grasps miss 
Looking forward to Smoke Flash at 22, would got it earlier but I took stam at 20
Dark Desire is having great laugh now
I'm playing my Necro/Poison as my second full-time MM and he's without a doubt as powerful as MZ ever was. In a different way - but powerful nevertheless.
I'm probably gonna see "Doctor Digitalis" go the distance and be my second L50 in almost 4yrs!
also might be interested in this poison (/thugs) guide from the US
My playstyle doesn't agree with the ideas of that player - I don't believe in a right and in a wrong way to build characters and thus dont like the attitude of that guide (which through the attitude fails to live up to the word "guide"). Still, the information about the powers is good.
Just remember all powers are good if you learn to use them. Except for /poison poison trap.
That power makes people want to say words that this forum would censor.
I enjoyed the idea of having it, but even I had to respec it out.
I have a Ninja/poison MM (Don't laugh, I actualy like to control thoses ADSD ninjas) Now I can clearly see the effect the envenom + Weaken is having on hard mobs (sadly recharge is tad slow, but that I can fix)
The heal almost seems a must, these Ninja don't get hit much, but when they do, they REALY notice it..
What i'm wondering is, if poison is woorth the going to 50, or would I be alot better off or more uesfull if I was /dark or /traps..
Dark - I can see its uses, cure all pets in one cast (if it hits) ae slow, ae fear, tohit debuff and other such goodsys. Down sides, these Ninja take alot of micro managment, unlike droids and every bugger and his dog seems be /Dark..
Traps - this set looks to have lots of fun possibilitys, seting up cool kill zones, sending in ninja to pull, then calling him back to watch the traps go off. Sadly no heal and I realy think I would miss a heal with these guys (heal has saved far to many group members too, as all these /dark casters don't seem to belive they can move in close before healing)
So how are you /poison guys doing and is there anything i'm not seing