Gw2 didn't have this issue, not even close, GW2 had some sever crash the first 2 days, fixed in.... 20/30 minutes? Then you could play for hours whitout any issues. And GW2 had (and still have) 2x the concurrent user online.
Diablo III sold 10x what this game will ever sold, still it wasn't unplayble for 10 days... yes Diablo III release was bad, 1 of the worst release ever, but NOT as bad as FFXIV ARR.