5 Stealths in one fight and attacking while stealthed?
I’m guessing you were in WvW. It’s a glitch. search the forum for “player culling” and you’ll find all sorts of posts about it.
Yes, it’s a known issue where the game itself is having a pretty significant delay for letting your client even know someone is there. It’s not only stealth, however. In some cases a normal player or zerg of players can be right on top of you before the game decides to draw them for you.
Now, about the 5 stealths. There’s no limit on the number of times a thief can go into stealth. The only real limitation is the “Revealed” debuff, which prevents them from re-entering stealth for a few seconds.
The engine right now is just a fail with larger battles. Even in PvE. A good example is the claw of Jormag in PvE. There are 80-120 people, but you never see more than 30-40 nomatter how long you stay.
And its getting so bad you can actually run past one anothers zerg or group before each one loads.
Its not only in WvW, I played some PvP with my guild mates. I played a stealth heavy mesmer. They said that I was invisible most of the time and sometimes they only knew that I was here was because phantasms spawned out of nowhere.