TDP is funky. TDP is actually the value of power used (averaged) in a specific series of apps. It's generally within 5°C± of the temp output, so was adopted as a value for temps and cooling. But it's by no means maximum power used or maximum temp output. Generally, you can figure max wattage as being @ 1.5 to 2x TDP of the cpu, with hyperthreading use figure 2x, and OC goes up from there.
The 2600x is a 95w TDP cpu. Running just 6 threads, figure a max of @ 140-150w rated coolers, like the 140w Hyper212, and that'll be adequate to keep Prime95 temps (non AVX,small fft) somewhere around 70ish. If pushing all 12 threads, start looking at 180w-200w rated coolers such as the Cryorig H5 etc, as that'd be 2x TDP± to keep 100% loads @ 70ish.
But that's just capacity. Efficiency is a whole different thing. The Cryorig H7 and the CM Hyper212 are both @ 140w, 120mm coolers and the Raijintek Aidos and Cryorig m9i are only 92mm coolers, yet anything below the 120w rating of the smaller coolers and all 4 have somewhat similar temps, the Cryorig coolers coming out with better, because they are more efficient.
So you can use the DR slim and see great temps, until you get right at its rating, then temps skyrocket. Meaning you'll get good idle temps, maybe even good gaming temps (gaming is usually @ 70% of max at best or 105w on that cpu) , and then do something dumb like shove Prime95 and close to 150w through a 120w cooler.
Ark: survival is an online game, as such its subject to changes, additions, DLC's, mods and other such, so it may not be your pc at fault, but might be entirely on the server side and what it's asking of the cpu.