Salutations Mustang,
It's nice to see you're willing to do the math on your skills and realize what's really worth maxing. You'll be disheartened by how many multizons actually dump 20 points into Multi for it's synergy to GA, despite those 20 points only doing like 8-11% of their final damage.
That aside:
1) The synergy between Stun and Concentration is only 10%ED, and while it's weapon-inspecific, you'll probably benefit more from a Mastery. Not maxing Stun will reduce your Berzerk damage by probably 20-40% depending on your stats (2-H swords gain 3% ED per str, so loosing 400% from Stun synergy might not be that big a deal).
2) If you're planning on using Berzerk on most bosses, then AmpDamage isn't important to you (except for CrushingBlow). With your curse option freed up, you can consider a curse to help you tank via Weaken or completely solve your ARating problems and possibly tank even better with BattleCry. Techincally Weaken or BattleCry (at lvl 25) both offer -50% enemy phys dmg, so can effectively double your life. Both are a lot stronger than BO in that regard. If you've maxed your absorbs, you might seriously consider maxing BattleCry instead of BO, but maxing both would be pretty damn strong (BO is a significant part of your +Life even if you've maxed Increased Stamina). If you get BattleCry to level 50 (-75% enemy dmg), then you have effectively quadrupled your char-screen listed life against phys dmg. BattleCry is the only skill that can do this.
3) Consider revising some of your chosen gear to include something with less than 185 str. I'm sure your offense will suffer a little, but I'm guessing you can do better. From the list you provided, it looks like elemental damage will cut you to peices, since your absorbs are pretty low. There's a post discussing
how important Absorbs are. Reading that post will make these suggestions make a lot more sense.
Consider these items for the reasons given (I'm not telling you to throw out your previous item list):
3.1) Leviathan armor (dr%, +30Str, Cleansing, high block bonuses) or Glassglare (Absorbs, pois reduction, low block bonuses)
3.2) Andy's Hat (pois reduction, low str, +30Str) or SteelShade (absorbs), or Ondal's Hat (Weaken, low level)
3.3) Don't up yor Gores. The defence boost won't even affect your To-Hit%, just sell the runes to Charsi if you don't want them, at least you'll get some gold. If your To-Hit% manages to change by 1 because you're right on the edge, then go for it.
3.4) TitanBlade for elemental bosses (it's pretty much the only weapon with absorbs, dr%, with 5%CBlow).
3.5) RisingSun ammy (absorbs).
3.6) WhispProjector ring (SoBarbs, -10%EnemyMagicRes, +10%ResMagic), or Nature'sPeace (Pois Reduction).