I agree with you OP, I really hated it. I admit that I'd thought Sirius/Remus was going to turn out to be a thing, but then it didn't.

However I didn't like Tonks anyhow, she just seemed like the most ridiculous character with a very sketchy personality, one of those irritating people who would just get on your nerves because they are so "wacky". There simply didn't seem to be anything in common between her and Remus.