Originally that was the case, but was revoked with new rulebook I think. You take all +'s and all -'s together and get the torp roll. If it's less than or equal to one, you get one.
So you could have for U66 R0 base of 3TT +1 WP +1Kondor -1 crippled, -1 Aerial ASW attack, -4 DD and you'd still roll one torp. Or you could have for U66 R0 base of 3TT +1 WP +1Kondor, -1 crippled, -1 Aerial and still roll 3 torps. .... Are you leaving the objective unclaimed! Heresy!