Cloaking before/during dialogues was a deliberate exploit to get around scripted combat encounters. The devs corrected it so you have to engage enemies the way they intended.
The cases in which you're allowed to cloak have already been fixed (or will be at some point) with the "mini contact" dialogues, which don't drop you out of cloak.
I swear, people like you who insist on sneaking around the galaxy are the only reason I'll never use the "mini contact" dialogues if I ever write Foundry missions. I'll use text popups before EVERY enemy group, then have them spawn right on top of you to make sure you can't sneak around them.