Exemplar is not an example of a great champion…
She was recently buffed as part of Patch 4.20 Void Rebalance. The changes introduced new mechanics for her A1 which now provide some use in niche scenarios. Whilst generally still not very useful in general dungeon/gameplay, you might find Exemplar useful when dealing with Iragoth, The Eternal Dragon in Doom Tower. Her ability to completly lock out abilities on her a1 whilst bringing a guaranteed weaken make her a viable option to beat the encounter.
Her a2 being on a 2 turn cooldown makes her somewhat viable for Fire knight in addition to the above and can bring Weaken to the clan boss if you can fit her into your Team.
All in all her buff did open up some options but Exemplar is still generally not useful for most situations.