I like the idea of moving away from a passive reward system. I don't mind doing something to earn something. I think the set pieces really need to be a "chance on drop" reward after completing an event each day. Like, if you complete 5 daily quests, or challenge someone in the arena each day -- you get a loot chest/bag/reward thing. In it could be a set piece, or gold, or ????

If you gate the set pieces to ONLY the top 50 slots in the arena, it will drive away players who -for what ever reason- are not, or can not get into those top slots. It will certainly make the top 50 slots unreachable for anyone who is not in one of those positions already. Those players will only get stronger with every new bit of gear they acquire. But if you make the set pieces something anyone could pick up.... then that playing field will get a lot more leveled. Then indeed, a lower level/new player might very well stand a chance of competing with/for those top slots.