I am the same OP. I have pld, smn, and drg all lvl 50 and in darklight gear or higher. Once you start the soldier tomb grind and the relic weapon upgrades it will become glaringly apparant that you just won't have time to gear them all. I chose my smn as the class I would continue forward with, concerning progression. Now I use my pld for fast roulette queues and my drg for random stuff once in a while. But all my progress for relic and soldier gear goes to my smn.