Mongwau combines the roles of huckster and shooter in the starting posse of The First Ring.
True, huckster 1 is enought to cast Blood Curse reliably in a deck full of 8s. Huckster 2 is slightly better because Paralyze Mark becomes more reliable, and Bobo gets stronger, but this is not a critical issue. Huckster 1 is good.
Now, although a 4R deck might be less aggressive than the Law Dogs or the Sloane Gang, it's still a good idea to have a dedicated shooter, a stud, in your starting posse, because in the current meta many decks play cards like Kidnappin', Bounty Hunter, and sometimes even Run 'Em Down. You don't want to be caught with your pants down, right?
In order to use Mongwau as a stud you will need some cheap spell fodder, like Forget. This shouldn't really be a problem because you do want to have lots of cheap and expendable spells in your 4R deck in order to play Hex Slingin' and possibly Magical Distraction, and to use your outfit ability.
The problem is that you can only use Mongwau's ability once per turn. So if your opponent sends Steven Wiles to harass you and you manage to deal with him, you're no longer able to protect yourself against his regular starting stud (or the other way around).
The other problem is that Mongwau will not protect you against that first click Kidnappin' if your opponents decides to remove him before you have a chance to teach him a single spell.
And the biggest problem is Shotgun. This card means that you actually cannot have your main shooter and spell-slinger participating in major shootouts. That's bad.
Now, all these three issues you have to keep in mind, but you can still play around them if you plan your battles carefully.
First of all, just stay away from battles that you don't want to get into. Lure the bad guy into a deed, then use Shadow Walk to run away, leaving him trapped there, unable to follow you. Of course, this will not always work, because your opponent is probably just as mean and nasty as Barton Everest. But smart use of movement can still win you a game that you would lose in a shootout.
Paralyze Mark will also help you keep that nasty dude with Shotgun at bay. If you boot him in the town square he won't be able to trade goods with another dude (cannot do this in town square). Just don't get into a shootout in this location, a booted dude can still shoot you dead (...dat sounded kinda like rap...)
If you won lowball this turn (or if you control Pearly's Palace), you can neutralize the Shotgun-weilding dude with Unprepared, Soul Blast, or Pistol Whip, before he get's a chance to shoot ya. Just hope your opponent doesn't play The Stakes Just Rose in the latter two cases.
If the opponent got you with Kidnappin' before you could pull your pants up (that is, learn your first spell), well... just give Mongwau to the wolves, don't try to protect him with the rest of your dudes. It might even be a good idea to just let the job succeed without a fight, this way you at least guarantee that he won't get aced, just discarded.
So, even though at first glance Mongwau looks like a badass, in truth he's quite fragile. But if you're smart and careful, you can outmaneuver all the traps that your opponent laid for him. And if not, well, maybe you should try Kevin or Tyx as your starting stud ;)