Should i go for Legendary Azura?

Well, 50 is probably not going to be enough.
Azura is a very strong dancer, but the problem with legendary hero banners is that sniping has a worse chance than in normal banners.

The chances of getting new year azura are higher

An other option is Young Azura, you can't get her yet but I think She'll show up in the next update to be gotten with heroic grails.
She's a pretty fine mage on her own, aside from sing.

Lastly there are Olivia and Sylvia, not the most special dancers but they are easy to merge up and to get the right IV.

If you lack dancers, go for it. If you're new or lack a particular niche (dancers, ranged cavalry, ranged or flying dancers, etc.) for event quests or battles, it's a good idea to try and fill those niches.

In the long run with recurring legendary banners, she'd be a very functional +10 in arena, as unlike other dancers she has a PRF assist. With a PRF weapon and carrying her own duel skill, she's banksy. (Especially as she's an excellent unit for the arena-support metagame.)

I'd pull if in your position.