Forretress has a bad case of 4 moveslot syndrome. Toxic Spikes isn't as useful anymore:
-Spikes/Toxic Spikes/Stealth Rock
-Rapid Spin
-Volt Switch
-Gyro Ball/Hidden Power (Ice)
Nature: Relaxed/Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Sturdy
Tbh, Sitrus Berry ain't useful competitively. While Pain Split is a shaky form of recovery, Rotom-W has no viable recovery outside of that and Rest:
-Volt Switch
-Hydro Pump
-Pain Split/Hidden Power (Ice)
-Will-o-Wisp
Nature: Modest
EVs: 184 HP/4 Def/144 SAtk/176 Spe
Item:Leftovers
You really should get with the B2/W2 changes, so Gliscor's SD set needs some changing around:
-Swords Dance
-Earthquake
-Acrobatics
-Substitute
Nature: Adamant/Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Flying Gem
Ability: Hyper Cutter/Poison Heal
I have a bit more I have to say but I'll stop here for now
OK, so I tried out some of your suggestions and have been doing a lot better. You were right, Toxic Spikes and Spikes aren't that useful so I switched them out for Stealth Rock which I then took off my Heatran and gave him Toxic. Heatran almost always makes the opponent switch giving me a free Toxic in there and then use Protect to get a bit of Toxic damage and to scout what move they want to use where I would then switch appropriately to resist the hit (predicting they'll go for the same move). As for Rotom-W, I tried out Pain Split but I didn't see myself using it that much and felt like Hidden Power (Ice) was a lot more useful. I also like Volt Switch better than Thunderbolt because it still hits pretty hard, and if it doesn't KO, I go to Forretress and Volt Switch again if I know I can resist that Pokemon. I also LOVE the Acrobatics Gliscor set. Flying Gem boosted Acrobatics has 1-Hit KO'd other Pokemon that RESIST it. I still stick with Poison Heal, though, as I can usually predict a Toxic for Gliscor to switch in.
Your suggestions are very helpful and I wouldn't mind more if anyone thinks there is something else that should be fixed up.