As he says, you can make it work. But unless there is a really strong reason for wanting to run this combination, I don't see it as a good choice. There are blast sets that work better with Poison, especially given that Poison's best power is PBAoE, you want sets that work well at point blank range. Electric and Rad would be my favorite choices, and Rad would look a lot better with Poison, I think. And Electric is a drain set, which works well with Poison Trap to drain AVs. Another option would be Dark Blast, which stacks its moderate -ToHit along with Poison's moderate -ToHit to end up with a solid overal To Hit debuff on a spawn. Both Electric and Dark can stack Holds with Poison so that Poison Trap plus the single-target Hold can Hold an entire spawn of 1 Boss and multiple LTs/Minions.
Basically, a good player with good design knowledge can take any set combination and give it good stats in Mid's. And a good player can play any such combination even when the set mechanics don't mesh well. But that player would still do better with sets that match better.
Lastly, I personally would never play Poison except as a Controller, because I think that the Tier 9 power is far better on a Controller than on the other powersets. I do have a very nice looking Electric Control/Poison build that should do well in AoE damage, solid in single-target, and great in control. And Electric Control has strong drains but not so strong in -Recovery, while Poison's trap is a great -Recovery power, so the two sets mesh together well for a max drain build.
Last part first. I definitely agree that taking /poison on a controller is definitely a stronger pairing. Elec. control/ and plant/ would be my first two thoughts there with Dark/ coming up on the outside.
And yes, I think that there are some very interesting choices that look to fit "better" in corrupter blasts. I think Dual Pistols would be a great fit for this but I've got DP ear marked for my Naff/DP defender. Ice would work very well too but that's going with time for me. That leaves Elec as a good mix in my book, but I've kind of settled on this combo.
Now as to why this combo? Well, when I played him on live, he was possibly the hardest hitting single target character I've ever rolled. Granted he was only level 23ish, but still could just cripple a boss or EB. The aoe damage will pick up in the later levels, but he'll never be known as an aoe machine.
Take a closer look at his numbers too: we are talking 47.5 % -tohit, 60+% -Def, 30% -Dam, 65% -rech, 78.75 % -Res, 275% -regen and a couple stuns and a couple holds. This is all before using BU. With BU you can really kick some of the mitigation powers into high gear (ie a 36ish second mag 3 hold in Poison Trap unless mids is wrong on the numbers).
Plus character concept. He's my Batman (or Moon Knight). The character who can't possibly do all the things he ends up doing. After all, he's got no real super powers. It's just this fancy suit (poison powers) and his rifle.
He even plays like that. I have to give some thought to what I'm going to do in a particular situation.
Sorry for sounding so excited about the combo but I can't get it out of my mind recently.