I cannot beat Mossdeep gym leaders. Psychic with Earthquake just oneshot kills my Pokemons, that are slower than enemies and even my most powerful Pokemon make very little dent for Claydol and that before it uses Light screen. Their Pokemon Lineup is:
Claydol LV. 41 and Xatu LV. 41 Lunatone LV. 42 and SolRock LV. 42
Spheal Lv.30 Surf, Ice Ball, Body Slam, Aurora Beam Sableeye Lv.34 Torment, Knock off, Faint Attack, Night shade Linoone Lv. 39 Rock Smash, cut, Dig, Headbutt Swellow Lv. 43 Steel Wing, Fly, Endeavor, Aerial Ace Swampert Lv. 42 Mud Shot, Take Down, Muddy Water, Surf Girafarig Lv. 37 Batton Pass, Confusion, Stomp, Agility
I have also few Pokemon that are pretenders in Lineup to change them (above team is not my default I made to defeat leader):
Torkoal Lv. 34 (normally switches out Sabbleye) Baltoy Lv. 27 (grinding up to switch out Girafarrig) Wailmer Lv.45 (caught recently, should I use him, normally I was going phase out swampert for spheal as I will grind it up as water/Ice Pokemon) Keckleon Lv. 32 (not using it). Castform Lv. 30 (not using it anymore).
How can I improve my lineup and do I need to do much level grinding? What moves should I teach Pokemons to defeat that gym?