(...) Actually there is no need anymore to play Knight imho. (...)
Agree on that.
I also saw warlocks tank on an equal way in (more or less) full mdps gear. So maybe one should nerf (which would always result in dislike and frustration) those non-plate-tanks so that they need to build some kind of defensive adapted gear for their classes, or give the knight class some better support. From my perspective, a knight should be more viable due to its support for the raid. Most knights already got some utility, but not all of them and most are pretty low. I mean, 5-12% more dmg on a target for XY seconds is quite nice, but doesn't matter at all in a raid setup of 10-12 golden geared players. If there were no events and immune phases, all the bosses would be burned down in seconds, so all those damage-buffing support is kinda useless in my eyes...at all.
Maybe knights should support the survivability much more? Maybe with more/better crowd control or damage reduction (for trash phases) since this isn't additively calculated anymore? Just like for example Knight/Mage (dmg reduction on AoE), Knight/Druid (shields and heal) and somehow also Knight/Champ (with its stuns) already do.