I fully levelled (50 plus incarnate etc...) a Bots/Traps. It is hard to explain exactly what makes it great but I do know a few reasons why it worked.
1) all the right debuffs in one place. Traps was given a very weak heal and was given outstanding debuff and damage in exchange. Acid mortar means that you will hit. Poison trap shuts down adds as well as most controllers and can wreck giant monster's health regen. Even the stupid seeker drones debuff accuracy, which compliments the defense granted by shield generator. And by the way, just throw caltrops and stand there. The AI poops itself and runs in circles everytime it steps on a Lego.
2. Shield generator. <-- it's really good. Mez protection is super important in chaotic fights. I played FF for a while and was jealous of the generator. Once it is out your endurance doesn't matter. It is clunky at times but so worth it. Bonus: when it blows up randomly at a quiet moment you get to watch your blaster friends freak out.
3. Aggro management. Normally, the MM draws hate by debuffing and healing. Traps confuses the AI. Acid mortar is a mini tank. Seeker drones draw fire. Occasionally something will pointlessly shoot at your generator. Poison trap lasts longer than the aggro list cares to remember. And as I said before caltrops can scare almost anything. Also, triage beacon is weak but it does not draw aggro the same way as AoE heals. The aggro managment makes you and your team highly survivable.
Traps are strange. Definately not for everyone, but they work really well. I never felt underpowered with bots/traps. I was an AV killing machine.