I had the fear of not been good enough when i first hit 50 on my War but i gave it ago and it was not as hard or as bad as i was thinking.

The party most of the time is more than willing to help out a new tank over any other role most likely since there scared they might drive you out and be forced to wait 40mins odd for another run.

As for having a hard time with relic +1 dps that can be a problem but i found if they pull argo they react by slowing down just enough to not steal the mob form you with out losing to much dps.

The big problem you will face and its rare is the bad dps that will not follow the marks and just unload on what ever they happen to target first making tanking a bunch of mobs tricky at times but that is rare.