Because of the attrition in GW, healing is key. Barriss is the best HoT plus a health boost. It was a reasonable question. She isn't NECESSARY, but if you are having trouble, she helps a lot. Luminara is a viable sub. HoT counters attrition.
Umm, shard shop makes all shard rewards valuable, especially shipments. Finishing GW daily nets 15 shards that can become over 200 shard shop currency.