I have the same issue while ingame (lobby too, but this is a different issue).

The Framerate drops to 1 or even 0 and the GPU load drops to 9% (i monitor it with Aida64 and my logitech keyboard). It goes back to normal after about 15sec or more. Killed me several times in dangerous situations.

I´ll attach the rpt as soon as i can.

I can confirm this issue:

• go to multiplayer, select a server
• join server

-> game freezes at class selection (cant use buttons or select a class or scroll down the window)

It unfreezes after up to 40sec.

Found something interesting today.

I just got a R290X, fired up ArmA3 and got over 60 frames on ultra settings in the graphic menu.

As soon as i went ingame (i played the Adept campaign - Scouting), the frames dropped to 25 and the GPU goes from 0% load to 99% all the time. I logged it with MSI Afterbruner. Here is the logfile:

https://mega.co.nz/#!IspjlISA!jQgeM1ctzb2LRwW4BROLzHYhb4oGrpYo9C3GsSctMhQ

the 25fps numbers are when i play ingame, otherwise it's option menu when i died for example.