1) is a shield tech build viable for pvp (do you actually have enough power to kill someone if you are wearing full Super Commando PVP gear)
Pay no attention to the naysayers, it's perfectly viable for 50 PvP. Yes, you have enough power to cause damage. 300k damage, 200k protection is not uncommon for me. Wearing a full set of Supercommando armor is pointless though, see #3 for the gear I use. PT tank damage is better than Jugg tanks, but still less than Assassin tanks.
2) what role do you usually find yourself playing, guarding nodes, guarding healers, running interference while others cap nodes or all of the above
You want to be in the thick of things, where all the action is. You have a lot of AoE at your disposal, including an AoE taunt. Run w/ a guild healer and toss guard around to protect your teammates. Be support DPS and help focus down enemies.
3) What type of augments do you guys use in your PVP armor, main stat? defense? absorb? endurance? power? or a combo of all of them, should I have more augments of one type over the other?
I use all Aim augments. I have tank implants, main hand, and offhand. The rest is DPS gear.
31/10/0. Take those 2 points out of Iron Fist in the Pyro tree and put them into Advanced Tools. The shorter cooldown on Grapple is well worth it.