I have something similar happen on pretty basic, all wired, tech.
Maybe not so coincidentally, it seems to happen at certain times when there is active spawning in Fel (and I'm a 99.9% tram ruleset player, only sneaking into Fel when I have to for T-Map digs, so it's affecting me in Tram, Ter Mur, Malas, Ilshenar, and Tokuno - I won't even GO to Tokuno when it's happening) and, of course, during events. In the latter, it's the worst, and my mouse moves so slowly that the boss that drops the monthly item is dead before I can even bring up the bar, even when the EM makes an effort to allow people to get the target bar before combat starts. This, on top of sporadic lag (worse than anything I've experienced since the first year of AoS) that is too specific to certain occasions (as noted above) to be purely accidental.
I think Broadsword might need to start checking to see if the servers now being cloud-hosted might have opened up an avenue for exploiters to artificially slow others' client response, including the client's mouse threading (which would be an overall symptom, not the main issue).