Damage splash numbers don't appear from the player's perspective. The whole reason why we can estimate with a fair amount of accuracy what the actual amount of damage reduction a player has running when others record videos of it is because we can see the damage splash numbers and compare them to what they would be if there were no damage resistance effects running.
Trick ran all the different legitimate sources of damage resistance in a post over two months ago and how they could stack. My post at #68 is basically a restatement of his, discounting for two glitches he mentioned that presumably were fixed with update 1.108 (concerning Thick Skinned, and the Machinist mod bonus). Understandably, Trick never went into great detail about how those two aspects can glitch but I sent him and Elizabeth a PM today to clarify as to the status of those two issues (although given what is going on right now I don't expect a response any time soon). The bottom line is that you can't explain more than 3 seconds of damage resistance at 79% or greater by pointing at any legitimage build. There has to be a game mechanic that is not working as intended for that to happen which is why no video is going to ever be able to legitimize what is being observed.

