Legacy comes at HM8 now if you wonder. There isn't much skill tweaking (as compared to back in the days though), you have "a build" and pretty much play this on 90% of content. Affirmentioned grad for example is used alot since debuff demage is a thing (can view it as "special skills while grabbed minus special skills annd more like dmg increase).
We indeed have class change vouchers, probably again with archer 3rd in march(?) <.- this just a wiiiiiild guess. Since bimonthly updated to the game april could be more realistic, then again march would bring spring trove so I expect archer 3rd to happen around there. So rn, no chance to switch, but let me ask why you want to switch. Especially (cutting nostalgic reasons short for a sec) you didnt play for long - maybe - you'd be better just making a new character to begin with. class change voucher is quite pricey if it comes along. and voucher is real money exclusive so, just be informed that changing class isn't the cheapest option [drastically changes though if you have like higher gear]
in a way only trove will give you hepta fuses now, but thats caused by the fact that trove rewards not really get adjusted as fast as we get new items. you can already fuse octa now, but thats really some topic you might be able to avoid on a casual play shedule. Don't get me wrong, octa fuses do have benefits. Their costs is in no relation to their increase in stats so one can just as easily skip them.
now it is more like pet gems which are almost unobtainable. then again you can get an rng box weekly and gable for either "low octa" or square (oh right, after octa itr is triangular, square, penta, hexa, hepta, octa now). But I dubbed "low octa" low since we don't actually have the "older" gems anymore. In fact soulboost even gives us penta gems (triangular for pet).