Griffons eye -lighting res now applies to traps in d2r, as where it did not in original d2.

In pvp scenario to have effective resistance against -20/-25 light resistance griffon you would need to have 195/200 lighting resistance to have 75res in hell?

correct. you would need to overstack light res to compensate for however much -enemy light resist your enemy is wearing. that can be quite a bit if they are running something like an elephant sin set up with an infinity or gear stacked with light facets.