Right now, your team has some major flaws:
- Your Magmortar's moveset is utterly abysmal in every way. Three Fire-type moves and Hyper Beam - Heatran would absolutely rip you a new one with a moveset like that, and lo and behold, Palmer has a Heatran. Your set is completely walled by Rock-types, and anything that resists Fire only has to worry about Hyper Beam, which is a poor move thanks to its recharge turn. Magmortar has a massive movepool to mess around with and a brilliant Sp.Attack stat to use with them. As a rule though, running two attack moves of the same type is a very bad move in 99% of scenarios...and this definitely comes under that 99%.
- Your team suffers from a terrible weakness to Water-types - all three Pokemon are weak to Water, one suffering from a 4x weakness to it. Encounter one Starmie in the Tower and your whole team is pretty much dead since it outspeeds everyone you have as well. You definitely need some protection against Water attacks here.
- Generally, you can do far better than OHKO attacks, since their terrible accuracy essentially means you'll be winging the Battle Tower relying on luck to win, which isn't going to get you very far nine out of ten times. Rock Wrecker on Rhyperior is again poor due to the recharge turn - two Stone Edges outdamage Rock Wrecker by a considerable margin, and one Rock Wrecker is all you'll get out of two turns.
Drop Hyper Beam and its clones - no good moveset should even consider running them.
- Look at your stats. Gliscor's Dark Pulse would be about as effective as using a butter knife to try and defeat a master samurai in armed combat since its Sp.Attack stat is awful. Timid is a poor nature for it as well since it drops your Attack stat and does nothing for Gliscor's immense Defense. Rhyperior's Nature is alright as is Magmortar's, so if anything I'd drop Gliscor for something that has Water Absorb or at least is resistant to Water-type attacks.
Sort out these more glaring issues with your team first, then we can move onto specific movesets and items.
