I think that it would be good to have Optifine in optional mods because it makes game playable for players without good computer (or with FPS problem even on good computer) and players won't need to download Optifine separately and install it.
Problem with that is a number of mods break down with Optifine added, so it would cause more problems sometimes.
You can download it yourself since it would be private, however, to add it to a pack, the pack creator would have to request it.
Actually I think that it would be enough to ask for permission as MYM and then distribute this mod through the MYM launcher. But all is on the mod author and admins.
Ok, thanks for information. By the way: What is definition of bigger modpack? Is Hypovolemia bigger modpack?
It really depends on the mods them self. Some are working ok with optifine others are breaking. Unfortunately I don't know which ones those all are. Anyways it can reach from graphical glitches to the client crashing.
i think its the botania shaders along with some other things in bigger packs like infinity that break the visuals, and cause some nasty litle errors, like people being in places they are not and storage inventories floating all over the place like madmen XD