T50 was not a good system, for reasons already mentioned, however:
I don't think arena is much better of a system, what arena does is simply prolong the farming, not necessarily make rares rarer, it's just as easy to get rares as it was before, just more time-consuming
I do agree that farming for rares is still just as boring, and now it takes longer
some system should be introduced to make getting rares harder, and taking more time is not harder, just boring and annoying