Hippowdon - your set actually looks pretty good. I run Toxic > Ice Fang, but that is just personal preference, also consider running Whirlwind.
Alakazam - I used Alakzam on my first Sand team, and I flat out love him. I have tried 4 different variations, those being Choice Specs, Life Orb + 4 attacks, Life Orb + Sub and 3 attacks, and Calm Mind + Focus Sash and 3 attacks. My favorite was Sub + 3 attacks by far.
Alakazam @ Life Orb
Trait: Magic Gaurd
EVs: 4 HP / 252 SAtk / 252 Spd
- Focus Blast
- Shadow Ball/Hidden Power [Fire]
With Magic Gaurd, you aren't taking damage from Life orb, Sand, any kind of status, hazards, etc. And you had better beleive this is abusable. Substitute protects you from being revenged by priority, specifiaclly Suckerpunch, Psyshock is STAB and hits quite a lot of things, Focus Blast hits Steel and Dark types mainly, that Psyshock really can't, and the last option, Shadow Ball hits Ghost types and gives you completely unresisted neutral coverage, as well as hitting 351 pokemon super effectively. HP Fire is another more reliable option for taking down Steel types, namely Scizor, Forretress, and Ferrothorn.
Ferrothorn - The set looks good, but what are you doing with the EVs and IVs? O Spd IVs isn't helping you, and you waste like half of your EVs. For a spread, go with 252 HP / 76 Def / 182 SDef
Terrakion - I am also going to be suggesting some minor things here.
Option #1: You have all that raw power, go with Adamant nature, you'll bury small cities. And second, Quick Attack > Earthquake, it may seem odd but the priority is useful for revenge killing weak opponent's that would normally outspeed and kill you.
Option #2: Scarf him and call it a day, your team could use a scarfer pretty badly.*
Scizor - I'll be doing basically the same thing here as I did with Terrakion.
Option #1 : If you went with Option #1 for Terrakion, give him Leftovers/Life Orb, and replace Pursuit for Superpower.
Option #2: If you went with Option #2 for Terrakion, give Scizor the following set:
Scizor @ Choice Band
EVs: 252 HP / 252 Atk / 4 SDef
- Bullet Punch
- U-turn *
Jellicent - I have been using this guy a lot lately and I quite like his bulk, and ability to run a baws support set. Use the following set:
Jellicent @ Leftovers
Trait: Water Absorb
EVs: 248 HP / 216 Def / 44 Spd
Scald is STAB and lets you get some additional damage on foes while they are being worn down by Burn, Taunt is very useful for trolling other walls such as Ferrothorn, Recover is for recovery (Surprise!), and W.O.W. cripples physical attackers, which helps support the team and Jellicent. the 44 Spd EVs allow Jellicent to Taunt, Burn, and Recover before many things that would usually outspeed and ruin you.
There's my 2 cents, overall it's a nice team.
If you see a * after the options on Terrakion and Scizor, it means that is the recommended option.