Big FPS drop after spamming Earthshatter & Warcries in the hideout

I'm testing out the attack speed in the hideout, with a build that uses Earthshatter + Warcries to explode the spikes.

My attack speed is still quite low, 0.80s on Earthshatter.

Warcry cooldown is negated by Warbringer ascendency.

If I spam Earthshatter and Warcries for a bit, eventually I notice the whole picture becomes blurry on my 1440p monitor, which is due to the Dynamic Resolution kicking in,

If I turn off Dynamic Resolution the FPS tanks from 60 down to 40-50. It seems it is stuck in that state and the FPS doesn't recover until the instance is renewed? I tried logging out and back in and as long as the decals still showed on the floor, the FPS drop was still there.

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Possibly related issue: when I start spamming Earthshatter and Warcries, within seconds I find that Earthshatter no longer display the spikes, only "gravel" animation is shown, yet they are being exploded by the Warcries.