Wall to wall is generally considered the standard. That said, if the party is dying because you can't keep up on healing, then the tank needs to be responsible and dial things back to what you are able to handle. Wall to wall pulls are only possible if everyone can handle them, which means the tank can mitigate, the healer can keep up heals, and the dps can burn. If you're in lower level gear as a healer, it's understandable if you find it hard to keep up, especially if the tank isn't mitigating how they should be.

On the tank side, I default to big pulls but if we have any issues I ask if we need to dial things back and then adjust to how the party needs things to be so we can succeed.

On the healer side, it doesn't usually come up but if someone asks then I tell them I can do either and pull as they're comfortable. I'd encourage you to at least try on big pulls so you can get used to them but don't be afraid to speak up if it's just a bit too much in a given party.