I am not an expert programmer but given that the new patch was meant to introduce the new Night Avenger AT and the multiple numbers of bugs especially of bosses which has popped up, it may be possible that someone has accidentally used/change an existing global variable/timer.
Let's think about it, some of bosses are spamming some of their attacks/heals far more frequently. Timer issues. I hear Warden Arcana spamming rifts, Gravitar spamming yellow bubbles, some alert bosses healing for ridiculous amount and some event activated mission to taking place.
With the original of dual blade and darkness nemesis vanishing, this has now expanded to quite a number of other power sets from the reports. Seems like part of the engine governing power sets are linked. I wonder did the dual blade and darkness problem came about together with some new power sets being introduced.
I am sure the back end engine is much more complicated and there could be more than just a few strings of codes that have gone astray. I am even wondering if it could be the some of the codes of the new Night Avenger alert which could have spilled over and cause this.
I beseige the dev team (new or old) to dig out some documentations or do some search checks of any variables you may have used with the new patch and see if they are surfacing in other parts of the game. Many are already complaining about too many parts of the game being bugged to a point they find it pointless playing. Myself, I just pass time chatting with friends, doing a bit of PvP (which seldom pops) and doing some lairs with expectations of them being broken for the sake of passing time.