I want to raise another alt, preferrably a Goblin.

1) Should i roll a shaman OR a warlock?
2) Also, is alchemy suitable for both of them?
3) If the answer to 2 is no, shaman or warlock benefits the most from alch?

shaman...if u like to heal.
warlock is great too. good dps. and theres not a lot of them. everyone wants u around to dps.

shaman is also good for dps tho, and you can heal yourself. i have both at the max level.

alchemy - very suitable for both of them..

benefits:

the epic trinket
transmute of gems and truegold

just make sure your 2nd profession is herbalism to make it easier to level your alchemy.

1) Shaman, (Heal/DPS) They heal great and Very good dps But warlock is also overpowered in dps, but iwould go with shaman.
2) alchemy Yeah, both can do alchemy but therees not a difference with the class with alchemy is the race
3) Warlock because alchemy makes potions and elixers and things so warlocks could use it more.

All in all i wold go with a Warlock, very overpowered dps also with minion.