As a huge fan of PvP tanking, I've always thought that the current implementation of the "Guard" ability, while good, falls seriously short of it's potential.
I'd love to see the "Guard" ability gain unique active skills that require guard to be up on a friendly target in order to be useable, as well as only being triggered in a PvP environment (unless they could be balanced for PvE I suppose)
For example here are some skill ideas:
"Amplification" - Overrides your shield generator control unit, increasing your shield and absorb rating by 100% (ie. doubles the current value, it's not added) for 6 seconds. Has cooldown of 2 minutes.
"Emergency Transfer" - Allows you to bestow your shield on a nearby friendly target, within a 10 meter range, providing a "Shielded" buff, which transfers your current shield and absorb rating to them for 6 seconds. While active your ability to shield is reduced by 100%. Has cooldown of 3 minutes.
"Shield Barrier" - Focusing on your guarded target, you channel your shield for maximum efficiency, reducing all damage done to them by 100% for 5 seconds. While channelling you are immune to interrupts but are rooted in place for the duration of the cast. Has cooldown of 5 minutes.
"Overload" - You overload your shield and that of your guarded target creating an ionic explosion that coats nearby friendly units providing 10% damage reduction for 6 seconds. Your previously guarded target gains the "Discharged" debuff and cannot be re-guarded for 45 seconds. Has a cooldown of 2 minutes.
The benefit to most of the above is emphasis on tanking stats, thus dps gear and hybrids would stand to benefit far less, hopefully creating a better place for mitigation based PvP tanks.
The potential animations for such skills could be quite epic too.
Disclaimer: These are just ideas... whether they are even possible or not, people much smarter than myself will know for sure. Durations and cooldowns were just added quickly for explanation's sake, as I'm sure they're far from realistic.
I'd love to see PvP tanks receive some attention and look forward to reading more in this thread!
Cheers