Hey! As someone who primarily plays as guild McMourning I think you starting list is pretty good list. My advice in terms of playing is don't be afraid to throw McMuffin out there right into the thick of things, particularly if you've got schemes that require a lot of mobility. People will see a tooled up Doc and often forget their game plans in the face of that many wounds and attacks. You can throw down with the best of them, I find (between your ridiculous number of wounds, hard to kill and the ability to self heal while still tearing your opponent apart).
Dr. McStuffin (I have many nicknames for McMourning) is also really good at switching tactics up, bouncing between direct damage, some buffing and straight up scheme running in the last turn, not to mention his poison shenanigans; though those opportunities may be less prevalent than a Resser Doc).
Grimwell is a guided missile of pain to most things - he's got a pretty ludicrous threat range and can dish out damae really well. I find he works best at either taking out weenie scheme runners or really big guns. For the latter, nimbling in and going lobotomy is a bit of a high risk high reward manoeuvre, but if you have he cards I say go for it, as it can often force your opponent to throw away big cards to avoid the Ml 7 attacks. As for the former, he can easily keep up with most scheme runners you'll see and tear through them like wet tissue, forcing your opponent to either burn through his hand to keep them alive or to push more important, expensivve models to deal with him or run schemes.
I find Nurse Heartsbane useful, but more situational. Guild does have a sore lack of control, which she does provide, and I will say one of the funnest (though not necessarily the most efficient) things to do is to throw out "Take Your Meds" (with uppers) with a Nurse followed by "Back to Bed Dear", meaning that the target can only take walk actions, and also can't take walk actions.
I love Guild McMourning, and I find the main thing to remember he is almost always a tremendous pain in the ass to deal with. Sure, he'snot inincible, but even for a Master he takes a lot of attention to pull down, and he goes down swinging