Tips for a noob Mastermind!

I recently got my Merc/dark Mastermind to lvl 50. I feel like I'm unperforming as my friend can solo stuff I struggle with. I was wondering some advice to what sets or IOs to slot. When comes to playing corruptors and defenders it's pretty straight forward as their my specialty, but Masterminds are something I've never really got, so any advice would be greatly appreciated.

I've never played mercs but here's some general advice.

Check out the Dark Miasma guides on the MM, Def and Corr forums, tons of good advice there and it all applies to you.

Do a search on "pet unique IOs", they make a difference.

Make sure your bottom tier pets have enough accuracy, remember they're 2 levels below you.

While Mercs is meh, DM is great just its self.

Almost every single power in Miasma helps Mid damage.

Tar Pit-Drop it on every spawn and with enough recharge you can double stack it.

Darkest Night-Use it on the biggest **** and watch is damage and ACC drop as well as those around em

Howling Twilight-No its not a rez its a AoE Stun that just happens to rez ppl also, Tar Pit+Howling Twilight=Almost AoE Hold like

Fearsome Scare-Drop a Range IO and keep most of the spawn scared while you make yer merc take em down 1 at a time.

Petrifying Gaze-Use along with the APP/PP Hold and bam you can hold boss's and with enough recharge even EB's

Fluffy-Oh fluffy, Heals/Fearsome scare/and Petrifying Gaze yummy stuff.

For the most part a */ DM mastermind is a */DM mastermind. No one is going to show you something that would be considered ground breaking. The wheel is already invented.

I would do a search for dark and look at what powers regardless of what the primary are that dark players are picking. I am pretty sure they are almost on par with a Dark Defender even. That would give you a feel for what players are playing. As an example I know Thugs / Dark is somewhat popular for thematic reasons.
"The bad guy with dark mysterious powers that leads a bunch of Thugs"

I would also post maybe your current build. What build your looking at to go to. What your money situation is. I am sure someone can post a 15 Billion IO build for you but if you can't even afford DO's whats the point. Right ?

The more you give the players to look at in this forum the more you will get out of them.

Do you also understand Defense Cap. How -ToHit buff works with Defense Cap. Basically some of the game mechanics that will relate to what your doing. If not say so I am sure someone will post links of stuff to read up so you understand that. The sooner you figure that stuff out the better off you will be.