Stay on current character. Not only can you then do whm but it will get a 50% xp boost until it catches up to your sch. Eye for an Eye, a arcanist spell at 34, is WHM's top cross class skill. I'd set it on your CNJ/WHM and use it that said, you may catch up to sch and decide to go to 50 on sch, or after getting 50 of WHM decide to get sch to 50; then either is far closer then if you restart.