So you want it nerfed to be comparable to our current set bonus?
Not quite. My thought process was that, as you also observed, that this is one of the strongest bonuses we've had. The consequence of being distinctly stronger is that it is more likely to be toned down, just as things that are distinctly weaker are more likely to be buffed.
Then there's the consideration of how spec's are balanced. I'm fairly sure that specs are balanced with their tier bonuses in mind, since it's typical for all specs to try and aim for 4p. So if Rogue DPS is and has been balanced with mediocre bonuses, one would expect the future bonuses to also be of similar level of potency.
It may be pessimistic, but it does have some rational behind it. There's many reasons why this could remain at 25% to a random stat for 30s every 30s, but there are still a number of reasons why it would be also be reduced in power. Both of them have reasoning behind them, but without being a part of the Dev team it's hard to say what their goal for Rogues is precisely.
All of this, of course, doesn't even consider the issue of how the EP value would scale past t12 content.