Well, this Mence can almost always 3hko Scarf Landog with even -1 Atk unstatused so I guess that's enuff reason to run Spe for it.
The only other EV nitpick I have is moving the 4 Atk and Def to SpD. All I kno this does is lower the chance of Mixed Mence to OHKO with Draco Meteor. Just a bit, but I'm not sure what those 4 EVs in Atk and def accomplish.
Teammates one idea I have is Mamoswine. Good synergy, and in particular it handles Thund which is very bad for this and really any Mence for the most part. Icicle Spear goes right through Sash Chomp which can otherwise win, and who doesn't want to break Breloom? It also beats the dangerous Gliscor, which can put Mence on a timer if it has Toxic, or more likely fish with Guillotine.
This Mence can deal pretty well with most Suicune and Cress, among other things Mamo dislikes like Rotoms and Aegi(no one likes Aegi.) It covers grass, water, and fighting weaknesses for Mamo, and isn't too bothered by steel for the most part. Mamo takes ice quite well and can switch in on t-waves and other electric moves.
Also top teammate for Mence, which is pretty big.
I think Heatran is really good with Mence in general, tho weirdly it's not in mence's top 20 teammates. It resists everything Mence is weak to but rock, and Mence is immune to ground and resistant to fighting and water. Heatran also really likes Suicune and Rotom-W in particular being removed. While this Mence likes being burned and doesn't mind fire moves besides, Tran's Flash Fire supports Ferrothorn greatly, another good teammate for Mence(#2.) Heatran is also pretty much perfect vs Mawile, which threatens Mence even if it can't quite OHKO at -1(tho it often won't be -1, and still can easily 2hko even if you go for Roost.) It's a full stop to Sylveon most of the time as well.
I think, given the nature of this set, some more exotic teammates than the ones in the top 20 for Mence are in order. Magnezone seems like a decent one. Mence covers all its weaknesses and Magnezone has an advantage vs Thund. I can't think of much else, but that's a decent enuff reason already, and remember we're trying to be fancy.