First 6* should always be your farmer in my opinion, with the first goal of being able to farm 12-6 brutal asap so that following 6* come quicker. I know that Kael is more than capable to farm 12-6 brutal geared in vamp set and also very versatile: good at cb, dongeons and arena. So definitely a good choice. Plus if it’s your starter you may already have invested skill tomes in him - thing to consider in my opinion.