I thought that VGs are suppose to kite as they are range or mid-range class.
VGs are the most functional at long range of all of the tanks (mostly because they're the only ones that get to regularly attack at 30m), but they still operate best within the 4m range: Stockstrike is the single biggest hitter they get and it comes up *all* the time. If you're not in melee as a VG, you're screwing yourself over.
The ironic thing about this is that, thanks to DS and Saber Strike dealing so little damage be being used so little by a top level Shadow, they have almost no real drop in effectiveness at 10m as opposed to 4m; every other tank sees deep drop offs when not directly in melee. Shadows can really just coast along with the occasional wasted GCD.
If I wanted to make a Tank for protecting healer in PVP (even though Rep healers are extremly rare these days), which class would be best suited for this purpose alone?
Guardian is going to be your best bet for that thanks to Guardian Leap: the other tanks only really have Guard to keep their healer alive; Guardians can Guardian Leap to throw a nice big survivability buff on their heal buddy (not to mention that it can bounce them over to their heal buddy immediately if they're pulled out of Guard range or whatever), not to mention the slows, pushes, stuns, etc. that they get. You're not going to do terribly impressive damage as a Guardian in PvP, but you can play interceptor and defense quite well.