how do u Shaman ?

Versatility is indeed the key word - I've used a lot of respec cards on this guy to try out the options you've already mentioned. I also did my 1st bronze solos with him. It's probably redundant to mention here since all the regulars here in the MP subforum have a lot of experience, but I would still recommend him the most for an entry level character; He's tanky and you can't really spec him wrong.

My most heretic build was to spec him without Shockwave. With a heavy shotgun, he has quite a long cooldown time, so it was just faster to shoot/melee enemies. Besides, he's a Krogan - leave all that fancy combo stuff to the Pyjaks. With Warp alone, he still has both a debuffer, primer and detonator.

I would recommend going for the Warp>Shockwave combo though. To me, that's what sets him apart from the KroSol/KroSent, along with some funny moments when you set off that barrier 

My Boring Shaman, the less boring bit is how I play him, I actually don't use my shotgun much outside of hacks (Wraith works just fine at most ranged), but my prefered method of dealing with shields is melee (so I sometimes spec 5a/6a fitness instead of passive), warp->melee->shockwave kills most non-bosses, and is in-your-face enough to justify for a krogan, whilst still being an adepty-boomy specialist. Ok, I lied, it's still boring. But RARWH-y!

Here's my standard Plat Build for him. I'll sometimes take Warp ammo, but I like to stick with AP for the piercing. There's also the cheese build or the Claymore build. I don't run a melee build on him as I always liked the BEs he makes. I used this for Awakening the Eye of Wrath.

Run a melee / shield regen / biotic explosion build. Barrier + Shield Power Cells makes you pretty tanky as you regen shields almost instantly. I use an acolyte + melee stunner to pimp slap the little guys the first few waves then strip shields/barriers on bosses. Have a wraith sidearm for armor and warp + incendiary cheese if necessary.

Not a score-whoring build but it gets the job done against every faction.

Shaman is just a much worse Human Adept. No real crowd control powers, no dodge, can't pack heavy weapons like other Krogans or his power recharge goes to shit. Never liked the guy.

I usually go 66644 or 46646, with Venom or Wraith, sometimes Graal. Love the bigtime BEs. Super tanky, very versatile. As someone else said, not a crazy score-whoring kit, but very reliable in basically any situation.

I drop Warp and go for a melee build. Claymore+Incendiary ammo to set up FE against armor and Shockwave to hide reload and detonate FE. Against mooks, Shockwave to stagger and melee for the kill.

Not the most optimal build but most fun build for me.

Soloing Platinum with HA is easier. Any Singularity can turn into a triple explosion. HA can hold doorways like a 300 pound gorilla. HA can hold shielded enemies from doing anything with Singularity. And if caught in the open - can dodge roll from something like Ravagers or Turrets, while the Shaman will eat all the shots and neither his health nor shields nor Barrier will prevent him from dying. Also, if a Banshee pops through a wall on him - he's done, if a Phantom manages to stagger him - he's done, Barrier explosions do not always work. His Warp seems buggier than the HA's, maybe cos of his size or short hands, but his Warp causes more problems to me. Also with HA, you can strafe from cover, cast Singularity and then detonate it trough walls with Shockwave, much more reliably, than casting Warp with a Shaman, cos Singularity has a huge radius.   

HA can biotic explode stuff from any range. Short, medium, long - doesn't matter, you have all the things covered, all the maps covered. With Shaman, all your Biotic explosions come from short range. 

The Shaman also comes with more sacrifices. If he wants to be a good melee character, he will have to forgo a lot of health, if he wants full Barrier, something has to go. Usually people will forgo passives. And without passives and with a Claymore his recharge on Warp in almost 6 seconds. If he packs an Omniblade - more sacrifices. Now, he can also use something light, like an Acolyte or Arc Pistol or Wraith - but FUCK that noise. I'm I a Krogan or not? MWRAAAAHAHAH! 

With HA it's simple. Go all out on Biotics and rek stuff. 

Long range BE's are very much viable with HA and easy to setup, Singularity - hold 2 enemies in place and even if some armored one passes trough it - he's primed, then Warp - BE. And if the enemy lingers around, he will get blasted by exploding Singularity at the end as-well. 

Enemies in cover are a cakewalk for HA. Any cannibal or trooper sitting in cover will be pulled out of it and exploded from range, rather than having to run next to the with a Shaman. Annoying enemies like Nemesis can be stopped from running around and wasting your time. Phantoms can be bated into a block stance with Singularity and when they leave it, they will be primed for a BE. 

C'mon guys.HA faster and easier than Shaman?Just try that challenge,which Alfonse posted in the thread with HA and Shaman,then we will talk.On gold probably(but not 100%)HA will be faster,but on plat the things are very different.On an open areas Shaman can survive turet,because he is fast as every Krogan.With HA you won't be able to use even an ops pack.If bashee teleports through the wall,both characters are finished.Sure,sometimes you can dodge.As for the phantolrolls,you have an ops pack.If she staggers you,just use it.Well played Shaman will be faster than HA.I can prove it if you want with two my solos.Same enemy,weapon,faction.Shaman was faster with 1 or 2 mins.

Both runs were on White vs cerb.I used wraith and despite the fact white is a perfect map for HA,Shaman was faster.