After those few, the difficulty kind of drops a tier.
I would say as far as **** hitting the fan (I present, a tier list on how poorly Bowser does against characters):
S
Sheik, Luigi
A
ZSS (Yoshi is somewhere in A)
A-
Diddy (unsure about 1.08 placement), Sonic, Fox, Pikachu, Brawler?
B
Rosalina, (ROB probably fits somewhere in here)
B-/C+
Other Throw combo XCopy characters (Mario, Falcon, etc. Standard high tier/top 10 junk), Olimar?
The only character I have no idea where to place is Kirby. The match up itself is actually a lot more difficult than you'd think, but rage just plays such an enormous role that I'm not sure.
Contrary to popular belief, the only projectile/zone characters you should have issues with are Villager, DHD and maybe Robin on a bad day. Samus and Link aren't bad at all.
Every other MU in this game is fairly manageable due to rage/limitations in mechanics. Even the worst MUs can be turned around due to a few bad decisions on your opponent's part. I can only rate the matchups based on feel of difficulty, it's hard to put numbers on things in this game. I would say it's damn near impossible for the first five-six characters I listed to make mistakes and actually drop games to us if they just play to their character's strengths.
Oh, and: PLEASE, DO NOT LOSE TO:
Shulk, Ganondorf
I don't know where to place the new DLC yet, and this isn't factoring in customs because I don't care about that.
I'm still pretty sure the biggest insult to a Smash player is to tell them that their character loses to Bowser.