Let's have another look at the torp/WB Defiant at 100 pts. This isn't to belabour a point (this thing has already been talked about so much), but rather just to contrast it in terms of alternatives.
Compare 2 Defiants to 1 Dictator, assuming a squadron and base contact for turret support and AC combining:
200 pts vs 210 pts
4 AC each, +50% hits to Defiants, -50% shields, -33% bomber attack run suppression.
67% torps & focusable firepower, no offside firepower, 90° turns.
So, the reduced cost, extra 4 hits and turn rate probably don't make up for the extra break points (3/6/9/12 vs 4/8), turret/shield loss and loss of total and focusable firepower. I think with a-boats it'd come close to being a viable option. Oh well.