I do not think any of the raids have been to bad, Most bosses IMO are not to crazy when it comes to mechanics (keep in mind I have pretty much only done heroic and a few of the starters on mythic)
I will agree depending on the week some M+ dungeons can be bad, Nokhud is a prime example before the dual boss. some of those large packs can be rough considering each mob has its own mechanic you need to look out for or interrupt on top of things like tornados, spirits, explosives etc etc. You can get some bad luck and wipe on something that is really no oneâs fault.
I understand the point of the affix as they are meant to spice the dungeons up in higher keys and make it so its not just the same grind for X months but I feel like they need to go one lane or the other. The dungeons themselves need to be dangerous with multiple mechanics to deal with or make it reasonable with the affixes mixed in.