DM/WP Scrapper

Good combo for what?

Survival? Yep, it's excellent for that.
AoE? Nope. Not even middle of the road, it's actually pretty bad.
PvP? I'd hazard a guess that it's not.
Soloing single tough targets like AVs? Yeah, shouldn't have much problems with some IOs thrown in.

World-class soloer, likely won't even be noticed on large teams.

Yes, it would. It would make a better tanker or brute than scrapper combo, IMO, though, just because the synergy is greater.

On a tanker, your chief duties are survival and aggro control. DM/WP is a Willpower tanker with a self heal. You are going to be pretty tough. Holding aggro may be harder for you, but you can always put more recharge in Taunt.

On a brute, your objective is to keep punching. You will have more than twice the base endurance recovery of most other brutes, if you also take Stamina. And you will still be WP plus a self-heal, so you're good to go.

Scrapper? This would be a good combination if you want to do things like solo pylons and archvillains. You will be tougher than most scrappers, and put out a lot of single target damage. If you routinely play on large teams, though, you will want a character with more AoE. My main /WP scrapper is Spines/WP, and that combination is pure joy.

You have to work a little bit to make a truly bad combo in this game. Unlike the prior posters, though, I'd say this is probably an average combo. If it fits your concept, go with it. If not, maybe consider something else.

Dark Melee is a single-target set with to-hit debuffs. WP uses a mix of defense and resistance with a lot of regeneration and significant boosts to regeneration when facing large crowds. The single-target vs. large crowd thing is where synergy breaks down, IMO.

Couple Dark Melee with a defense-heavy set and you get some great results. If you go */SR, for instance, you would get that synergy and have a nice global recharge bonus to go with it, helping you build a great single-target attack chain. If you have the influence and time, you can buy/create sets to take */WP to the softcap for several types, which will be even more effective than */SR (global recharge power aside).

Going the other way, pair up */WP with a more AOE-heavy set and you get great results. Katana, Claws, Broadsword, and Spines all have better synergy with WP than DM, IMO.

Again, DM/WP is still okay. WP is arguably the best survivability set in the game, so you can pair it with anything and be fine. I just believe you can get more out of DM and WP by pairing them up with other sets.

i would disagree... heartily.

DM only sucks at AOE/PBAOE, as a solo target damage type it's one of the best.

Doubled with WP and you get the best of both worlds... as DM's best stuff tend to be end heavy, WP makes up for it, DM's best abilities require a lot of people around to fire up, WP gets stronger the more people around. DM's problem is it doesn't kill crowds fast, WP's strength is it gets better in crowds so it doesn't matter how slow you take them down...

finally, WP is weak vs single target AVs, while DM covers for that inadequacy with a massive self heal and a lot of single target damage.

Finally, when built right it can even rock in pvp... of all the WP based pvp builds i've seen the strongest have been WP/DM hands down, as the single target heals and massive single target damage allow it to trade punches with the most elite regen scrapper duelers on nearly equal footing.

I Co-Sign on this notion being a dedicated Regen/WP user and having a DM as my first toon ever made during Open beta of CoH that I still have.