As long as you're not skipping a plate upgrade because you went with a scale set 2-3 lvls before reaching the next tier that's fine. But those sets do have a lower PDEF/MDEF rating per iLVL than plate so you're not gettign as much bang for your buck. Realistically I wouldn't expect someone to upgrade every 3 > 2 > 3 > 2 lvls but if they do, great