Sucker punch is fairly useful, but it doesn't outweigh the benefit of dual-wielding. Your physical tank should be the one knocking people down anyways.
A CC and debuff rogue is a bit counterintuitive, since most (if not all) scoundrel skills are designed for up close burst damage. You'd basically have a mage with relatively useless melee skills.
Scoundrel+necromancer is a great combo since you get healed for the damage you deal and you can add some useful skills, like bone cage and decaying touch. Necromancers get a lot of debuff skills as well, so it might be up your alley. You should also pick up some skills in pyromancy, like haste and clear mind.
