Shieldtech is not really viable in PvP. Yes you will be more suvivable if you use a set of defensive super commando warhero & spec shieldtech, but your damage will be so much lower that you will not be able to burst anyone down effectively. That isn't your aim obviously as a tank, but unfortunately in SWTOR's pvp bursting critical players down as fast as possible is king.
The things most hurting is that defensive stats (be it defense or shield/absorb) are only about 50% effective in PvP. Defense and Shield only works on melee & ranged attacks, but not on force & tech attacks (roughly half the classes use mainly force or mainly tech). Yet you pay the same amount of stat allocation points for them.
So if you get an item with +20 power and +20 crit, those stat points boost all your attacks in pvp, i.e. they work 100%. But take an item with +20 defense and +20 shield rating, and those stat points only boost your defense against roughly half the incoming attacks.
So what this means is, that when you face someone in full DPS gear while you wear full Defense gear, they will have a massive advantage over you if they have one or more main attacks that are force or tech based. And if they don't, it will be equal. That is hardly fair.
What I would advise, is if you really want to play a supportive role, still get an offensive war hero set, spec either AP for more damage or Shieldtech for more survivability, but do not believe Bioware's old promise where they said all specs are within 10% dps of one another...if you spec Shieldtech your damage will be 20-30% lower than AP or Pyrotech. Using Ion Gas Cylinder with AP works pretty well and allows you to guard other players while stilling dealing a respectable amount of damage.
You can use a shield generator, but know that even with Ion Gas Cylinder active it will provide a mere 2% damage reduction on average (20% chance to reduce damage by 20% on 50% of the incoming attacks = 2%). Without Ion Gas Cylinder it will provide a mere 0.5% damage reduction (lol). On the other hand a power generator will provide you with roughly 200 more techpower, which should be around a 5% boost regardless of what cylinder you use. Again defense vs offense is not in balance.