They reduced the requirements on unlocking the actual races, but not the sets. You don’t need the achievements, you just need the levels to unlock the races now.
The only change they’ve made to Heritage (that I know of) was removing the Reputation that Mag’har never needed anyway.
I only have one account, but I already have like 370 or something mounts (usable on 1 character) on this one, and there is no way I’m farming all those again on a second account, so I can’t say I’ve ever had this problem. Lol