Who tanks?

[Terkhev]

if you're new/don't know the content, maybe ask one of the other tanks if they wouldn't mind MT'ing

While it's natural reaction, I'd say opposite should be the way to go. Outside of savage content, MT doesn't have to do anything. OT on the other hand needs to do some important mechanics in few fights, especially now with normal raids roulette.

Personally I try to adjust to sync and players. For example if I'm on lvl 50 WAR I'll try to MT because of no Deliverance and OT when I'm on DRK. If I see other tank(s) are PLD I'll pull.