There's no difference in page drop % I can promise you that. RNG happens in mysterious ways
After backflagging multiple groups through Tier 6 and above, each group would always get dicked on 1-2 different pages than the group before it. It's just the fact that you miss 1-2 pages of the set, and have already begun looting the repeat pages on other toons so you get further behind on that same page. It feels as though it's super rare, but I promise once you grind a few hundred runs, it'll even out for the most part, just because of how many different pages and rolls you'll get down the road.
ToV scales on the other hand... are forever a piece of shit. You'll most likely never catch up on the color you get behind on first. I think I was roughly 15 red behind upon finishing my first UCv3, then it jumped to 30... then 50... then I caught back up a good bit (and ignored looting green scales for a couple days)
At one point, working on my 6th UCv3, I think I had finished Green Scales on the toon before even looting a single Red Scale on him, and he had around 60 Silver Scales
The mathematician in me says that one day I'll even out, you can't argue percentages ! But EZ server RNG has its own special numbers system. Basically, Hateborne gets home every night and rolls some dice, then mashes in that RNG sequence, uploads it to the server, and laughs at all of our misfortune.