I'm confused, what's the problem again...?

Your FC leader was a healer
Tank was doing baby pulls...
Tank messages you telling you that your FC leader healer is toxic?

Did your FC leader flame him?

I'll give them the benefit of the doubt, maybe he was too scared to ask or he was being rushed despite being uncomfy. Perhaps he tried and got a bad response, there's alot of missing context.

When I was new I was fortunate to play with someone who is an experienced healer, she gave me alot of confidence in early dungeons and I always wanted to see how far I can push it so I communicated with healers back then. I was always more scared on a healer than tank because in other games I always heard in MMOs that it's always the healer's fault, so I never really played healers or tanks.

I think being mindful that people might be in that stage of building confidence or are still scared/anxious to pull more and forcing it just gives a negative experience. For me I might just say 'you can pull more if you're comfy' if they do it, great, if not I'm fine with it too.

But yeah it has nothing to do with you, but I'm suspecting that guy didn't have a good time....I think blocking your FC leader should've sufficed.