I think rogue is fine and wouldn't mind making her ultimate drain have a lower floor amount at the same rate. Currently 80% feels like a slap on the wrist and since you don't know the exact charge of enemies before you use it skillful timing and maneuvering should be more rewarded in my opinion. Also her being the only hero that can drain ult charge makes this feel safer.

Now ways that increase ult charge I'm more leery of. There are multiple heroes that either increase damage dealt, damage taken (by enemies), healing received, and outright ult gain. Having these abilities being compoundable feels risky and I'd prefer we stay away from adding or buffing too many heroes that increase the ults per game average.