Hey man, Alomomola is a great poke, nice choice to start a team with!
I don't think it needs magic coat however, as its main use was for countering Deoxys-D and Deoxys-S hazard leads, but those are banned now, so I reccomend using Scald instead. I've also got some EVs for Alomomola from a friend to maximize its bulk, allowing it to take both special and physical hits easily, basically making it very hard to OHKO, or KO in general.
Alomomola (F) @ Leftovers
Ability: Regenerator
EVs: 36 HP / 220 Def / 252 SDef
Calm nature
- Scald
- Wish
- Protect
- Toxic
Anyways I agree that the 3 steel types are a bit redundant, but this team actually doesn't appear to be weak to a whole lot. I think you might be able to cover more threats by running M Venusaur over Ferrothorn and replacing M Mawile with Clefable. Clefable and Aegislash combo [though I reccomend running 144 atk evs on Aegislash, as well as either Shadow Sneak or Flash Cannon over Sub, to better function offensively and break stall] will act as your stallbreakers in wake of replacing mawile. M Venusaur better covers Rotom and LO Thundurus [who could take out a few pokes with proper prediction, as it 2hkos aegis after SR] and strengthens your defenses vs almost every sweeper. You'll have to change assault vest to lefties and put SR on Land, though. Other than that I think the team would function a bit better this way, although it might open you up more to Land-I, although I think you could play around it.
SubToxic already lets Aegislash handle stall:
-Substitute
-Toxic
-King's Shield
-Shadow Ball
Nature: Modest
EVs: 244 HP/12 Def/252 SAtk
Item: Leftovers
Here are better all-out attacking sets for Aegislash:
-Shadow Ball
-Shadow Sneak
-Sacred Sword/Iron Head/Pursuit
-King's Shield
Nature: Quiet
EVs: 244 HP/12 Def/252 SAtk
Item: Leftovers/Spooky Plate/Spell Tag
or
-Shadow Ball
-Shadow Sneak
-Flash Cannon/Pursuit
-Sacred Sword
Nature: Hasty/Naive
EVs: 4 Atk/252 SAtk/252 Spe
Item: Life Orb