Shield Bash for 0 AP every turn and with extra damage from all possible sources (including Combo if I recall correctly) was really quite good
Shield Bash counts as neither unarmed nor fist weapon attack and in fact interferes with Combo. I have never paid much attention to the interaction before but can now tell with certainty that any melee attack besides unarmed and fist weapon simply nullifies the existing Combo stacks, so doing something like punch - slice with a knife - punch will leave one with a single stack of Combo against the target. The same goes for Shield Bash.
From looking at your response I'm assuming that the build you played was DEX combat gloves with Shield Bash flavour (an unarmed build would not go for more than 12 DEX at absolute most and would prioritise STR instead so it has to have been combat gloves, right?..). The problem is that DEX gloves is perhaps the strongest melee build in the game and has no need whatever for Shield Bash, as pneumatic hammer does the same job more than once per turn and is infinitely better in comparison. Such build is straight up weaker with Shield Bash than without, as the bare minimum of feats required to make Shield Bash worthwhile could be spent on feats further improving ordinary attacks, which are arealdy far more effective to begin with. That's not to mention having to overinvest into STR as you say and being stuck with an armour type that serves the character very little purpose besides featuring a shield. What I played, on the other hand, was an unarmed build with only 9 DEX and the rest in STR, built primarily around Shield Bash... and yet even this build would have been much stronger without it! Having 5 of my feat slots occupied with Shield Bash and its synergies - Boarding Up, Shield Arm (lol), the feat itself, Nimble & Body Weight Training for Lightning Punches - forces me to give up on such feats as Critical Power, Recklessness, Improved/Expert Unarmed Combat, Bone Breaker (lmao even), Escape Artist, etc., as well as more crit-oriented Infused Rathound wife-beater overcoat. Basically, the difference is that the build you played was, as it appears to me, a perfectly self-sufficient
and pretty much broken build that benefitted none from the inclusion of Shield Bash, while I played a build expressly centred on Shield Bash with the intent for it to be the build's focus and the main source of damage (yet with the way it is Shield Bash was only dealing 10% to 15% of overall damage at best, and even that solely because it was compromising the build's ability to deal damage by dint of its very existence).
Based on all of the above, I'm going to make a bold claim that your view of Shield Bash being decent as is is heavily skewed by the potency of the build it was included in, and which in the first place needed it little more than a sixth toe. My suggestions were made from the position of wishing for a build that could employ Shield Bash as primary means of damage, with ordinary attacks fulfilling a supporting role of stacking Boarding Up and re-enabling the main
hero of the story means of offense, as opposed to bashing a single target to death and killing ten more conventionally. I would not say that Shield Bash is completely awful; unleashing a decently powerful sledgehammer swing once per turn per 0 AP isn't the worst thing in the universe (I mean it beats Spirit Poison). I have enjoyed bashing the shit out of many a foe quite a bit, yet nonetheless, for all the investment stipulated by Shield Bash, from feats and specs to equipment and high enough level, it simply doesn't do anywhere near enough to justify its inclusion, whether in a supporting or a primary role, besides want of flavour on a whim.
