Having any regeneration makes benefitial for waiting long times between taking any risk in new fights (exploring new parts of the map or stepping into the teleport to a new map). I think the game shouldn't reward us for just doing nothing and waiting.
For preventing the waiting before stepping into the teleport would be the simpliest by adding a time frame for maps. E.g. 6min. After that you won't be regenerated by your regeneration stat. For preventing the waiting if you executed the map before 6min we should gain the leftover regeneration amount (time until 6min) while teleporting.
And for preventing that making benefitial to just run back to the spawn and waiting for regeneration before the next combat, regeneration should stop after 20s of the last kill you executed.
The item Last Stand should also have an activation limit per map (e.g. 4 times) for the same purpose.