I'm not entirely sure I understand what you're asking, as it kind of rambles along. You ask me to explain something, but then don't actually ask a question.
For the specified gear set and, for the sake of comparison numbers (what you seem to be running into in the latter half of the above quote), Faith+Bruiser vs Calcitrant+Tantra (also, /war with Berserk up in Abyssea, and accounting for ODD):
F+B melee/ws split: 57.4/42.6
C+T melee/ws split: 57.2/42.8
F+B melee punch/kick split: 90.9/9.1
C+T melee punch/kick split: 90.2/9.8
So, more damage from weaponskill than you estimated favors that which increases total damage (Tantra) over just melee damage (Bruiser's). On the other hand, less damage from kicks favors Bruiser's over Tantra.
Varied DPS comparisons:
Set 1: Abyssea (capped acc)
Code:
Ear
Neck None Tantra Bruiser Aesir Moonshade
None 431.206 432.302 432.166 433.367 439.183
Agasaya 433.607 434.71 434.568 435.769 441.569
Calcitrant 435.223 436.364 435.946 437.153 443.179
Faith 433.367 434.469 436.981 435.528 441.33
Rancor 442.207 443.332 443.189 444.417 450.138
Set 2: Outside, 90% hit rate without neck/ear
Code:
Ear
Neck None Tantra Bruiser Aesir Moonshade
None 160.615 161.125 162.585 161.769 163.66
Agasaya 168.223 168.755 170.208 169.205 171.102
Calcitrant 162.792 163.325 164.933 164.072 165.803
Faith 166.391 166.756 170.256 167.565 169.312
Rancor 168.987 169.482 170.954 170.136 172.014
Ziel 168.239 168.77 168.694 169.343 171.251
Inside Abyssea, Rancor wins by a wide margin, as does Moonshade (att/regain version, btw). The next best options are Calc/Aesir, Faith/Bruiser, and Calc/Tantra. Agasaya is on the weaker end of things, along with Faith without Bruiser.
Ouside Abyssea, where accuracy matters at least a little, Rancor is brought back into line with the rest of the options, being only barely ahead of Ziel and Agasaya. Moonshade is also a relatively weaker option since weaponskills don't get quite as much of a boost.
Calcitrant is far weaker due to the lack of accuracy. Faith is also on the weaker side unless paired with a Bruiser, at which point it's on par with the other top contenders.
Obviously, the best choice depends on both the situation and what gear you actually have available to you. Inside Abyssea, top choice is obviously Rancor Collar; lacking that (or not wanting the +damage taken), I'd go with Calcitrant. Outside Abyssea (and needing acc), I'd probably just stick with Agasaya for solid, all-around performance, assuming that if accuracy is an issue I probably don't want the +damage taken of the Rancor. Though if base hit rate dropped to 85% or so I'd switch over to the Ziel (which doesn't show its full benefit here, as you only need 10 acc to reach cap).
Outside Abyssea on older content you'll be capping accuracy, so it would revert more to the Abyssea set in terms of relative standings, though the margin that Rancor wins by will still be closer to the second set (ie: very narrow advantage).