Much of the frustration with the "tank meta" is how effective it is to simply hold block. With no specific investments in blocking other than equipping SnB, you can easily hold block and repeatedly heal to full (usually healing numerous allies in the process) for a good 10-15 seconds at a time minimum, while reducing incoming direct damage to nearly nothing. Very rarely will your 32k HP be bursted down in the second or two it takes to recover from an unblockable stun. All it takes to refresh your Stamina pool is a tri-pot and a defensive ulti.

Because of the rather unfortunate necessity of "perma blocking" in high end PvE tanking, balancing options are limited. Giving everyone access to an unblockable stun (Turn Evil) is a good start. However, the nerfs to PvE mass healing don't even address the PvP headache of full tank builds effectively healing entire zergs while holding block on their SnB bar, with no specific investment in healing itself. Rewarding such low-effort gameplay in this manner discourages players from developing their skills and instead encourages zerging.

Luckily, there already exists a pathway for mechanics to be scaled differently in PvP versus PvE without changing their core functionality. Battle Spirit could offer some combination of increasing block cost, decreasing block mitigation, and/or reducing healing done to other players. This can even be handled differently in CP and noCP PvP, and there are probably even better solutions out there that I haven't thought of! Either way, stacks of tanks healing each other makes for tedious PvP, so something needs to change.