It’s never as simple as buffing or nerfing a whole class or build. You have to look at it on a skill-by-skill/trait-by-trait basis, which is what the design team usually does.
The design team is also good at looking at the bigger picture in terms of increasing the viability of builds that currently don’t see much play.
Technically speaking, nerfing is generally easier to do from a design perspective because overpowered things tend to be more obvious. It requires a little more effort to buff something that is weak.
Ultimately we’ll see a mixture of both buffing and nerfing like most balance patches. The only question is when.