lotsa dark malts will increase your ph toward the acid side, which can give you those harsher flavors. i think it will also accentuate the hops sharply.
i don't think you used too much dark malts, just not enough base malt. with two lbs of roasted/dark malts, i'd aim for about ten lbs of pale malt. that way you are not above 20% adjuncts.
and definately give the stout a spell, even if only two weeks in the secondary.
the last stout we made was on xmas eve, it was as follows
ten lbs pale malt
one lb chocolate malt
one lb roast barely
two oz ekg full boil
we are just now cracking the bottles and it is a smooth, silky, malty stout. it takes a long time mate