Since when was it the Tanks job to explain fights?

[Waeksyn]

Frankly, tanks are probably the worst to explain any fight mechanics because they are usually dealing with different things from the rest of the party. Attacks that only the tank has to deal with and ensuring defensive cooldowns are done at appropriate times, tank swapping, boss positioning, etc. Healers see all of the flow of the fight and probably need to be the best informed overall.

That said, the person who should explain a fight to a newcomer is the one who a) knows the fight and b) is capable of clearly describing it. Just being the tank does not necessarily qualify you.

And, to support the OP, if you are in a party and think someone is not doing a good job at explaining things, then step in and make the corrections - or - STFU.

[Granyala]

Healers see all of the flow of the fight and probably need to be the best informed overall.

Erm.. no. Not at all.
Do you know how many fights are "dodge random stuff on the ground while watching the bars of the group/raid frame" for me?

As a healer it's VERY easy to sort of "trance" through the encounter, not realizing what others are doing.
Often I "wake up" when the damage stops coming in, asking myself "what's up? Oh.. boss is dead already."
It's a really weird place to be in.

My experience: Ranged DPS has the most time to observe (long casts, basically 2.5 seconds with nothing to do) and the best overview.
Melee is usually in front trying not to get a seizure from the spellgasm, tank nibbles away at the bosses big toe while seeing fuck all because giant leg in his face...

I agree on the explaining part though. Whomever knows stuff should do it. I do it all the time. If a newbie asks a question, no matter how ridiculous it sounds, I will give a short answer if I know it in order to help.