Put it his way.
If you go into PVP with a DPS build you can have a DPS race to see who wins with the fastest TTK (plus gank fest).
If you go into PVP as a tank, they will apply far more damage than you can mitigate and you'll never gank anyone.
You have no way to mitigate the incoming DPS to even out the contest.
The game simply isn't balanced in any way to make PVP tanks viable (unless they are DPS tanks).
vis-a-vis.
Anything other than a DPS build is pointless for anything other than a PVP rear gunner on the back line.
And as a tank doing low DPS, that makes you worthless.
Healer in the background, is always required.
Perhaps in 12 months your tank will face your DPS and stale mate.
Until that happens you want to be a DPS.
heartbreaking for me..but that's the reality.
Especially when 1.7 hits.
People can combo hit you for way more damage than you can resist.
Its as good as one shotting people at the moment for all intents and purposes as you cant defend at all either way and death is certain.