TLDR: Big % changes do not matter if you buff abilities or passives which do no damage to begin with. A simple 5% buff to Mortal strike or Execute would be more effective in rectifying the poor performance of Arms on Single target boss fights where they struggle.
My thoughts for each buff:
Increasing cleave damage is ok, but unless they also buff the bladestorm build, cleave still won’t get picked much. The ability is very reliant on Merciless bonegrinder to compete with Improved sweeping MS and tier procs. That build is held back by the atrociously low damage that bladestorm does, the ability is only used to get Hurricane and Bonegrinder buffs, that needs to change if they want to see Arms warriors play with Bladestorm and cleave again. Without any changes to bladestorm, cleave is only just used as a backup to spread deep wounds.
Dreadnought being buffed by 30% is good for both AOE and ST and probably the most meaningful of these changes from a raiding perspective. I am 487 iLvL and dreadnought does 9,4K (before mastery buffs). A 30% buff is roughly (1,3X9,4k=12,2k) which is a 3k damage increase, which amounts to a 7,5% increase in the overall damage of overpower (3k/40k=0,075). How much is this for a bossfight? Best case scenario using one of my best logs on M Volcoross (99 Parse) as an example, i did 232,7k DPS where overpower was 13,41% of my damage. That is (232,7kX0,1341=31k) 31k DPS, if we add the 7,5% (31kX1,075=33,3k) we get 2,3K extra DPS under the best circumstances in ST on Volcoross.
The deep wounds buff is comparatively worse. I have 25% mastery, so my deep wounds do 34k over 18 seconds, which amounts to (34k/18=1,8k) 1,8k per second. A 15% increase for deep wounds using same M Volcoross log as before, where deep wounds did 3,71% of my damage i can calculate the damage it did to be (232,7kX0,0371=8,6k). Where the 15% would give me (8,6kX1,15=9,89k), so roughly 1,3k DPS for that M volcoross.
The last buff is also primarily an AOE buff, the damage this change would bring to ST boss fights is so low that i won’t even bother to do any math, but to give you an idea. This effect only procs when the sudden death execute happens. My thunder clap does 12k damage, if you increase that by 200% that is still only 36k (12k increase from the buff), which is good for AOE, but completely worthless for ST. The proc is sporadic, but typically happens every 5-20 seconds. It would yield maybe 200-500 DPS over the course of a fight.
So how much better would my DPS be on that 99 parse M Volcoross? well, if we add them together (2,3k+1,3k+0,5k=4,1k), it puts my DPS at (232,7k+4,1k=236,8k) which is 1,7% increase in DPS under optimal circumstances. That is not going to help Arms at all, this buff is lip service at best and bewildering considering how much some of the other specs were buffed, especially those that were already significantly better than Arms. I do not recommend playing this spec.