With the nerfs to any and all skills that grant Major Expedition, combined with nerfing all sets and potions that grant it too, you've basically killed this buff in PVP. Pots are now super situational, basically useless for 3/4's of the cooldown, so nobody will run these. Sets are very niche, and often require killing things, so only certain builds will run these. That leaves skills, which the 4 second duration makes a huge pain to maintain throughout a fight. Your goal was to make it harder for people to maintain Major Expedition, what you actually accomplished was making people simply not run it outright.

I propose increasing the Major Expedition duration from skills to 8-12 seconds, making them more in line with other buffs, and in turn increasing the Major Expedition duration from potions to 24-32 seconds. I would also propose adding a magicka variant of the potions, so magicka builds have something to work with outside of skills. Doing so would still make it harder for players to maintain 100% uptime on Major Expedition (impossible to do with potions alone, actually), but doesn't make it completely useless by not fitting within the buff rotation.