Lets face it, no one likes them. atleast in early game(who wants to fight multiple tier 3 or 4 enemies when youre in wood or copper armor) . instead of having it be a global thing where you hide away in a 1block by 1 block hole for 5 minutes, make them actual storms. light storms can be small and fast. for likely to catch you off guard but will both pass by quick or be easy to run out of the path of if you do spot it ahead of time. heavy would be much larger but slower. making them easier to notice ahead of time but also requiring effort to either evac for the time being or prepare and hunker down.
As for surface instability, nobody likes it. it always gets in the way of good build spots for no reason other then fuck you. it could either be scrapped entirely and focused into the temporal storm, or make it associated with something like ruins, or be an indication of something underground, and if you go to the ruined location underground and wreck it, it removes the surface instability or something. another possibility would be being able to use temporal gears to cleanse an area on the surface of the temporal instability