u talk about game technical problems, i talk about design of patch itself
MoP has worst idea for launch, dailies mandatory for at least few weeks, and having crap raids didn't help it either
WoD has the most successful launch even when ppl were unable to start Garrison because it spiked the most return of wow players, a problem that can be solved in few days
TBC problem was first time ever all those ppl in same zone, again problem is NOT game design, wait few weeks and u can log safely
MoP on other hand problem didn't start get fixed until next patch, with reduce dailies importance, increase reputation gained, give alts massive rep buff (they never repeated that), and so on, problems that need a patch to fix, not a technical server-side problem to fix unrelated to patch
So you are right that TBC has worst launch of technical lvl, but i'm talking about patch quality itself, not technical problem
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they aren't amazing but they aren't bad either
however Theramore scenario specially is way underwhelming, too bad for a pre-patch event