Only generally against teams that had horrible goaltending and/or poor defense. Holtby is an aging declining 30+ year old. Any time your save percentage is below .900, you're mediocre. Luongo last season before he retired, his save percentage was 0.899 (still higher than Holtby) - first time in his long career he hit that mark.
As to the issue of 'who will be the backup'. Ain't that hard to sign a journeyman NHL vet goalie for a fraction of Holtby's cap hit. Use the difference on signing an additional depth defenseman. IMHO, we'd be better off overall with that option.