I think that Expertise did work with armor spikes at some point but it no longer does. Also armor spikes or serrated blades stack, meaning if you use more than one you don't get additional hits or bleed procs but only higher damage so it never really pays off to use more than one each.
Metal armor is still a very good choice for a gloved fighter, not because of Expertise but because of the sturdy vest you can use with crafting. For metal armor the additional hitpoints you gain equal 100% of the vest quality so theoretically you can get up to 160 HP. This is a huge amount for a level 25 psi brawler with 3 con and thus only ~ 175 HP. It's somewhat rare though so you'd have to check the shops regularly. The quality of the vest will only influence bonus HP, metal plate will still determine the armor penalty and the defense stats so Armor Sloping + Nimble + <20 armor penalty is mandatory. It's achievable with Supersteel and max one serrated blade or Tichrome and no blades, and you don't really need any as you can proc bleeding with gloves.
DEX used to be on par with STR when it came to total damage output per turn (incl. critical damage), maybe even better. Now that it got nerfed, STR wins so try to keep it as high as possible. You don't need more than 10 DEX for metal gloves anyway. 16 base AP will go down to 13 AP and Lightning Punches + tabbis will finally bring it to 10 AP what equals 5 hits. In order to get 6 hits you'd need to get down to 8 AP per hit and it's not achievable with less than 14 DEX. That's 4 stat points you'd need to take off from STR which would equal loss of 40% weapon damage bonus, just to gain 20% damage through 1 extra hit - absolutely not worth it, even more so if you take the loss of weapon skill into account -> less damage and precission.
Also with only 5 hits per turn, both Expertise and Fancy Footwork don't really pay off so just stick to 6 AGI, Sprint and Recklessness. The later will significally quicken your Bone Breker procs which will stack up nicely with all mechanical damage including that from Force Emission. Combo is much weaker since the latest patch, maybe not entirely useless but there is always a better choice. Penumatic gloves and Power Fist can guarantee incap so skip Combo. Expose Weakness on the other hand is a must. Because of 3 CON it might be a good idea to wait with PSI atleast until you're done with Depot A. If you go for it earlier you can still manage but in that case I critically recommend to use a vigorous belt (+30 HP, - 2 AGI) + burrower burger (+1 CON) + pig leather tabis (+1 CON) if you happen to find/craft them. Hint - Blaine always sells the tabi recipe and sometimes even a Tichrome plate. You'll get there before level 12 and if you happen to get Tichrome (plus a sturdy vest), take +1 INT and Armor Sloping on Level 12 and craft the armor.
Before that, for a PSI glass cannon that bit of additional HP with extra CON and the belt can mean the difference between life and death, especially if you happen to step on a mine. Speaking of which, invest alot in traps skill BEFORE you step into Depot A and use antithermic/blast gear when walking around those minefields (even if it ruins your stealth) or you're likely to die from one single blast.
Crafted metal gloves are ok but they can't compete against the
Power Fist. That thing is seriously OP. Late game, together with rathound barbeque you'll end up with 17 total STR which also equals 100% additional Power Fist melee damage. Untill you get it, it's probably better to use crafted leather gloves (1 shock, 1 pneumatic) + eel sandwich. 11 DEX is enough to get down to 6 AP per hit resulting in 8 hits/turn. Once you get the Power First use one of the two unique leather gloves as the secondary weapon - the Claw or the Ripper's glove. The latter is superior when you have the serrated supersteel armor and easy time stacking and keeping Taste for Blood alive. Bear traps are also awesome to get TfB flowing as all it takes is one single bleed wound to start stacking.
So to sum it up, statwise best go for 10+++++/10/6/3/3/3/5+
Feat progression I'd recommend:
01 - Sprint
01 - Recklessness
02 - Nimble
04 - Lightning Punches
06 - Quick Tinkering
08 - Cheap Shots
10 - Bone Breaker
12 - Taste for Blood
14 - Critical Power
16 - Armor Sloping
18 - Wrestling
20 - Vile Weaponry
22 - Expose Weakness
24 - Corporeal Projection
[Edit 19.05.] Replaced Opportunist with Critical Power as the crit chance with only 10 DEX is still worth the extra damage. Opportunist on the other hand is less good without Combo which I had to remove in the first place.
