if your a blaster you would most likely be flying and away from the battle useing eld spear.
Why would you need DR watch is the only think that seems good from them feats. if you get mith armor you can get med armor without a feat or if you go battle caster you can come out with heavy. you get a fast healing once a day if something realy gets to you. if anything you sould focuse on your saves with gear like vest or resistance and spell strike weopen. Even some feats help with this like force of personality or the kiss feat from BOED. Useing defence invocations would help more at this point then the DR so getting extra invocations like Devils own luck, Ignor the prye, Entropic warding, or enervating shadows.
at least then you can chose to max your blast then qucken another or if your just a caster type you can get ability focus and turn everything into a chicken charm the chicken and cook it on a wall of fire.