I think a balance is better. You don't need to pull wall to wall of course, but never pulling more than one mob group at a time is very slow except for maybe brand new healers. I'm still quite new myself and playing as a WHM. A wall to wall pull is stressful for me still, but the tank never pulling more than one group at a time feels much too slow to me already. It doesn't have to be something you put pressure on yourself to do instantly, but I would work toward it rather than just staying slow intentionally. I think you'd wind up having more fun yourself actually.