In our case, the low frame rate is always associated to glitching and flickering.
We also realized that not all the players are affected at the same extent. Few did not complained at all.

@danczer: We play with game level set to Elite. Hence, we always play in First Person and the FPS drop found was definitely consistent.

No idea about Third Person game.

Yesterday evening we had a mission on Stratis and no FPS issue was found.
We also updated (manually) BattleEye, as suggested here.

I'm not sure to state either it's a map-related problem or BE problem.

@DnA: The session was in Takistan (not Chernarus as stated before).
However we had no issues on the mod map. Big problems were found on Altis.

All the player and server as well were updated tu the latest release 1.48

EDIT: We're planning other missions (which were working fine before) with others maps either mod or vanilla.
I'll give a feedback ASAP.

Hi there.
I'm from an Italian community (2RGT) almost 40 players wide and we experience the same annoying problem. Normally we always play modded Arma 3 on a regularly updated server.

Immediately after the update we noticed a global FPR reduction in any situation and occasionally a huge trop to an unplayable level of 3 FPS. Relaxing or rebooting doesn't help.
Furthermore there's an increased tendency to ArmA crashes, especially in low FPS moments (almost 15 crashes in an evening, honestly too much).

The mission we played yesterday was exactly the same we successfully played last week, without ANY FPS drops or crashes.

Two days ago we played in Chernarus (another previously played mission) and no huge FPS drop was noticed.

EDIT: The second mission was in Pakistan, not Chernarus. :-P