No, those feats are blatantly overpowered if ported over to D&D. They do not address whatever weaknesses you perceive warrior-types to have in D&D, they just make warriors more powerful against each other. And all a fighter needs to deal with a spellcaster is 1) winged boots or the like, 2) cloak of resistance or the like for Will saves, and 3) possibly a Periapt of Wisdom for additional Will save reinforcement. And at low levels, none of that is needed (the Iron Will feat will suffice).
Now, as I said, I don't know what other feats or combat system changes that book Swashbuckling Adventures must have, but if Brawny and Giant were imported to D&D, they'd be blatantly overpowered and most warrior-types, at least, would take them at 1st-level (and probably play humans to do so). From your description, Brawny is better than the DR a barbarian gains over the lower to middle levels, and available right away. Giant is better than Weapon Focus, and possibly equal or better than Weapon Specialization, and Improved Grapple, combined, plus the addition of 10' reach. I don't know if SA is meant to be a higher-lethality setting (than D&D) or not, but changes like this would seem to indicate such.
If you haven't seen a warrior-type in 3E D&D yet who could kill a spellcaster in one hit with little trouble at all, then you just haven't seen any decent warrior build yet. Or a warrior-type who could ping a spellcaster to death easily with archery.