Without looking at your numbers specifically, I find that this type of analyses are usually misleading, grossly underestimating what a minmaxer can do with the -5/+10 mechanism, thus severely underestimating the power of these feats.
In short:
these feats are completely broken but white-room analysis generally doesn't see it.
Again, I haven't looked at this particular set of numbers. But I can ask you all - do they crunch the numbers for the following scenario? (If so I will be impressed, no other similar analysis have even come close, and I will happily admit that my previous statements then do not apply in this specific case
But I am not holding my breath, the math gets complicated, much more so than most white-room analysts are prepared to deal with.)
Case in point (and please excuse any mistakes with details; I'm doing this from memory here): Battlemaster Fighter using a -5/+10 feat in conjunction with advantage, possibly a bonus such as Bless, and the Precision maneuver.
Obviously no serious analysis would make the error of computing average damage without taking into account that using GWM/SS is voluntary. Lots of flawed efforts add in the negative impact of using -5 when enemy AC is too high - I am assuming this is not the case here.
You should then use Precision to turn near-misses into hits. Rolls of perhaps 1 thru 5 will be left alone (accepted as misses), with advantage this happens much less often than 25%.
You will find two things: a) the miss rate is really low, despite -5 b) you don't use nearly as many superiority dice as for other maneuvers (you don't need to spend a superiority die on a hit or a clear miss, only near misses)
This makes you come close to the full potential of +10 damage per attack, and good sustainability of the tactic (you can expect to use it for a large portion of the day's important battles).
If this poster's analysis shows that GWM/SS grants between +30 and +50 damage at medium- to high levels for a properly minmaxed character, congratulations - that matches my actual play experience.
It also proves beyond a shadow of a doubt that these feats are completely broken in expert hands. Nothing else in the game comes close to granting you a potential +10 damage, and the -5 can be played around, as shown. WotC's designers must be less than expert, or they would have caught and stopped this.
Have a nice day.
Zapp
PS. If you have any questions, there are very many and very long threads about the subject. Every piece of data you might require is there. DS
