You have no idea how bad this is for ranged builds. If they implement this garbage, the adrenaline charged slayer arrows, whose damage gets applied to 4 arrows on every burst when manyshotting, will now only get applied to 2.41 arrows: that's an immediate DPS decrease of 44%. If they nerf slayer arrow on top of this, that's going to tip the scales to well over a 50% drop in DPS (assuming they take only 6% damage off of slaying arrows, which they won't; it'll be more than that) and represent the single biggest nerfing, not just in ddo, but in video game history! No one, in any game, ever, has taken so many quality builds and just chucked them in the trash heap. This is the most authoritarian, heavy handed, "we just don't like that some people are uber" approach to video game management that I have ever seen: it reeks of the lack of long-term planning.
Calculations.
Now:
MS = 20 sec * 4 arrows/sec = 80
10k = 60 sec * 2.75 arrows/sec = 165
Nothing = 25 sec * 1 arrow/sec + 15 sec * 1.29 arrows/sec = 44
Total 289
Proposed (using Tensors for full bab, which is annoying so kindly change that to char level):
MS = 20 * 2.41 = 48
10k = 60 * 1.89 = 113
Nothing = 40 * 1.29 = 52
Total 213
Your math is wrong: the manyshot nerf alone is a 44% drop in DPS right off the bat. So what percentage of 4 arrows does a reduction to 2.41arrows represent (arrows being the vehicle for damage, so while they decreased the damage by 26% percent, they also decreased the number of vehicles by 44%...in addition to everything else).
Ranged builds lost the 20% damage bonus from archer's focus, the expanded crit range went down to a +1, and now this? It's beyond nerfing: it's straight up trashing ranged builds!