Our mage in timeless isle/boost gear with no enchants did fine
The insta boost gear for some classes is awesome - great itemisation and really good stat budget. Didn't keep all the pieces for my druid but the neck piece at least had a better stat budget than any other piece at 468.
The stats an item loses from a socket are more than made up by the fact that gems aren't scaled down in challenge modes, while the rest of the stats on your gear are (except for hit/exp, obviously).
The other stats are scaled down more to make up for that, so that's not the reason you want gems. The reason you want gems is that they are budgeted with only 80 main stat and 80 secondary stat, which is less than you get from a gem, and the socket bonus.