Tanking is easy on any class that can tank. in my experience if a more single target based tank cant hold aggro of trash its because the party is too stupid to adapt.
to the notion of "no kite tanking" for champions: NO tank should do that. its insane. ~5to 11 other partymembers moving and repositioning themselves aswell - watching out for frontal aoes, boss specific events...thats just chaos. now if the mob in question has an aggro drop or you loose aggro due to whatever other reasons...you are most likely running away from the mob you need to reaggro before he hits anyone else..... kiting has no place in endgame bossfights. (repositioning the boss is different then kiting.)
why knights are complaining: no k/x can dps - there is NO way to play knight and have a role untill you can tank. And since ur dps is so low, you cannot tank unless u equalor outgear anyone else in party!!
with dps and heals the falloff is gradual - ur not as good as everyone else but meh u still do your job.
you cannot "tank a little less" then everyone else in party. with wd/w and w/k and possibly (hey we dont know, those skills arent final yet) champion you have more dps (more solocapability) and more single target aggro sooner.
with a mixed population of players between endgame geared and not quite dod ready - you start beeing usefull to the party alot later as a knight then any other class.
That beeing said... i love my endgame knight ...warden and champion dont interest me in the slightest