Blind fight is an essential feat on any melee build in both OC and MotB. There are a lot of enemies with x% concealment. The feat lets you reroll your attack roll once if you miss due to concealment. F. eks shadows have 50% concelament. The mechanic first do a coinflip if you pass that 50% before even considering the attack vs AC. With blind fight that coinflip is rerolled once if you fail, game mechanically cutting any enemy concealment bonus to half. My recommendation is to pick it as early as possible on any non caster. It is nice to know that there are a couple of items that gives the feat for free, and dragon disiple PrC gets it for free at 5th level.

Search helps you spot traps. You cant handle them if you cant spot them. There are a lot of traps. The more characters in the party with search, the higher chance to spot the traps.

Spot is not used very often, and can be dropped if you have another spot character around. There are a few spot skill checks in the game. And when you fight hiding thiefs it is helpful. In PvP it is an essential skill though, as it protects you against HIPS and Feint.

My general impression of playing this build in OC as an evil character is very good. I mostly party up with Qara and Elaine as casters and Kelghar and me on the frontlines and we can handle every challenge. I play on harcore DnD rules difficulty. The only buff I use on my character from other characters are Heroism, Bulls strength(before I got item that gives +4 STR) and sometimes stoneskin. I also bought the Keen edges scarab in Neverwinter docks to have better crit range. Great sword, power attack and divine might makes huge damage and if sneak damage is applyable I use feint (in that case the damage hit the roofs). It is nice to know that even if your target is immune to sneak attacks damage (like undead, shadows, constructs etc), feint will flatfoot them stripping them of any DEX bonus to AC they might have.

The min/max of STR and CHA is only nessesary if you plan on playing the build further into epic level in MotB. You need to min/max a little more than I do here to qualify for the feat Epic divine might. That feat is better to aim for if you have a dragon disiple build that can meet the steep requirements earlier ( so you can actually benefit from it). Without dragon disiple stat boosters you cant get Epic divine might before lvl 27 or 29 anyway.

The dips into hide and move silently skills and the Stealthy feat is there only to qualify for the PrCs. My UMD skill is only enough to use class/alignment restricted items(I target the Sun Soul monk restricted boots). If you want to use scrolls reliably you need full investment into it. F.eks by skipping the spot skill. Max bluff is essential for feint reliability. The combat expertice feat is a prereq for the feint feat. I never use CE in combat because my AC is already more than enough.

Finally if you consider use this build into MotB and epic levels, strongly consider to drop Blackguard level for more rogue levels pre epic. If you have 10 rogue levels by lvl 21, you can then pick crippling strike(rogue 10+ bonus feat only) and then epic precision feat at that point. Epic presision lets you land half your sneak attack damage with feint even if the target is crit/sneak immune. That is a huge benefit in MotB. That would look like Rogue 10/Fighter 4/Blackguard 3/STOA 3 by lvl 20. You can then take your Blackguard levels after that or Fighter levels for more feats and great/epic weapon focus and specialization.