If you want most possible damage, fire melee is the winner, beats BS by a longshot imo, however it doesn't have any parry skill which is very nice defense.
With fire melee you will be able to take down a boss in under 10 seconds, with a few crits, then it'll be down to 5 seconds, which is very likely (I seem to crit all the time).
Have no regen though, so i do not know if you need defense with it or how good your survivability will be.
I have a lvl 34 BS/WP scrapper and a lvl 34 fire/super reflex scrapper... Fire is a lot more fun and a lot better.
DM/Regen is stupidly easy to survive on a great burst damage. That said BS/Regen would probably be equally as good. Fire Melee would beat the above two on AoE but it depends what you want to do.
With the up coming changes to DM you'll have fairly nice spike damage from Midnight Grasp too, which is all neg en and thus fairly un resisted (though anything that does resist it REALLY resists it)
Of course from all the scrapper sets claws does the best damage over time if you keep followup perma (which isn't hard really).
It depends on what you want damage wise. Spines is without a doubt the best AoE, fire is good AoE and ST and then the best ST damage depends entirely on your situation
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
Notes on my BS/Regen at 41:
- you're going to need Hasten. And when you start collecting IOs, pick up Damage/Recharges.
- BS/ seems to need more help with Accuracy / ToHit than some other sets - I've cranked most of my Acc values to 60% or higher which gives a pretty acceptable hit rate.
- Parry is very effective. Solo or in small groups you'll rarely need it, use it every couple of attacks against larger groups or bosses. Remember it has no Ranged or AoE def, though, so try and pick up a +DEF pool power at some point. Even Combat Jumping helps.
- the much-maligned new MoG is very useful for taking alphas from large groups or bosses, but it runs out much faster than you think. With any luck you'll have far fewer enemies to worry about by that time.
- get, slot and love Head Splitter. When you're working with a skilled herder tank, lay one into the middle of the group followed by Slice and half the minions will fall at your feet.
Is it time for the dance of joy yet?
From the viewpoint of a Bs/Regen main
Broadsword is a pretty good all-rounder. It has the hardest hitting spike damage attack that a scrapper can get and it has some handy secondary effects too.
You get two Knockdown/Knock Up attacks, both of which do masses of damage and make for some useful soft control. Almost all your attacks debuff defence and you get a 5% base accuracy buff which puts only Martial Arts ahead of you in the accuracy stakes.
Parry can soft cap your Melee defence if you slot it for defence and recharge and use it every couple of attacks. It's great for switching from an offensive to defensive fighting style if things get nasty and you need a few seconds to recover. Combined with the Knockdown from Headsplitter and Disembowel you get some pretty decent protection to back up your Regen.
Only Katana, and to some extent claws, can provide you with this level of mitigation in a scrapper Primary set. Dark and Martial Arts can match it to some extent but Dark does it by debuff rather than knockdown and Martial Arts uses a couple of unpopular Stun attacks.
Hasten is useful for Broadsword/Regen as it works well with the self heal clickies and for putting your attack chain into a higher gear.
If you like fly then Air Superiority is a good pool attack to get. It makes for a handy soft control in the early levels and it only really needs slotting with 2x Acc or 1 Acc + 1 Recharge. Later on you can juggle Bosses/EBs with Air Sup, Headsplitter and Disembowel.
Now MoG is effectively a protection version of Build Up it is also great for foiling Sappers and Ring Mistresses in the 40s. If they miss you first time around then they're pretty much dead when you get in melee.
I'd recommend against taking Fire as a primary for a Regen scrapper. What it gains in damage output it loses in mitigation. The same applies to Spines and, to a degree, Dual Blades. At higher Rep levels Regen needs a little something extra to cover its weak Defence and Resistance. Keep in mind that if you can't somehow manipulate the enemy with knockdown, stun or acc debuffs then they will hit you fairly easily and for full damage.
If you take DB, Vengeful Slice and the Sweep chain (1000 Cuts > Power Slice > Typhoon) both have useful knockdown components. But while Sweep can flatten an entire circle of foes, the time it takes to work up the chain is a factor.
DB also has great -Def AoE debuffs available from Ablative Strike and the Weaken chain (Slash > Ablat > Typhoon) to let you clear mobs quickly, particularly if you're working with AoE-friendly blasters like AR or Fire.
For raw, one-on-one AV-flattening damage, though, BS still rules.
Is it time for the dance of joy yet?
The problem I find with the knockdown in DB is that it comes at the end of the attack. Venegful Slice has something like three ticks of damage before the knockdown takes effect. 1000 Cuts takes even longer. It's only short period but I find it leaves my Db/Regen very exposed. In comparison targets hit by Broadsword and Katana Knockdowns would be just starting to get back up by the time the DB's knockdown effect triggers.
DB users in teams rock because of their blistering pace and AoE effects, but one on one with a Boss I'd rather have a Broadsword. 
Oh and something that needs mentioning, with the sounds and looks disembowel is the only attack in the game that has made me wince. Its one of the reasons why Broad Sword stands head and shoulders above Katana and DB in animations in that it looks and sounds more real
"Well, they found my diary today.
They were appropriately appalled
at the discovery of the eight victims
They're now putting it all together.
Women wrapped in silk
with one leg missing
Eight legs, one body, silk,
spider, brilliant!"
Hi, im looking for regular hero players to suggest a good /regen scrapper, i been hearin alot of good things about Broad sword/regen but i want to be able to do tons of damage and go the distance in long periods of combat without dying, so is BS/regen the way to go? or can someone sugggest something better?
I want to do lots of damage, stay alive and hopefully not have to wait too long between rechgarges.
thanks in advance :O