So my question to more experienced tanks, would cybertech help much in AoE tanking for a Guardian?
Since the grenades can only be used once every 3 minutes and are on the GCD, they're not really going to help much. You'll get some help on one pull every 3 minutes, assuming they're clustered but, beyond that, it's not really going to do much.
Last question, how big a deal is Biochem for a tank, like it you had a VG with it and a VG without biochem stims, how much a difference does it make?
Biochem isn't a vastly necessary as it used to be, but it's definitely one of the more useful from a gameplay standpoint: when you're not doing progression content , the fact that you've always got your Rakata stim and you can never run out of your medpac or adrenals, which is always nice to have. It's going to save you a *lot* of money in the long term and probably be the most useful when doing dailies, but, honestly, all of the crew skills are a wash for progression since nothing is really better than what you're bringing in already.