Guild Wars 2

I noticed that in the past few WvW games that there are some mesmers that can control their clones that actually do damage. (Or so it seems)

Ill paint a picture.

I was behind a gate in our tower by the supplies location. (It was being attacked by an opposing world)
I alt tabbed to take a look at a few things on the guild wars wiki. (How to get the secret treasure that the tutorial was talking about)

Came back and I was dead.. Not sure how that happened since I didnt think anything could hit me or even reach me. Figured maybe a catapult or something hit me luckily. (yea I didnt think to check combat logs)

Ran back to tower. (Was close to spawn) and managed to get back inside again. I didnt alt tab this time and after a few seconds. I saw 2 illusions headed towards me. They went through the gate and came charging at me. The sword one and the one with the ranged staff.

The guards did nothing to them and they were hitting me for around 1-2k each hit. I died.

Checked my battle log and saw that I died the same way last time.

On the 3rd time going back to the tower, I saved my stealth (Used it to get in the tower originally) and ran into tower. And of course the 2 illusions came after me again. I cloaked by the supplies and they ran towards the main gate and started attacking it.

As soon as I uncloaked they stopped attacking gate and started attacking me again. I was like WTF. Turned around and killed them both barely, only to find 2 more of them appearing inside and charging me. Dead

Those things hit like trucks and had so much HP. And were smart.

Anyone able to tell me if that is actual game mechanics or if that was some sort of exploit?