Can anyone explain how DPS in catform works with a druid? Is it better to use a slow or fast weapon? Or is cat attk speed normalized?
Druids in either cat or bear form pick up 2 Attack Power per 1 Strength. Add to this that when in cat form, an additional 1 Attack Power per 1 Agility is also picked up. Druids have always had this ratio since the game first launched.
Animal form attack speeds are fixed and not changed by actual weapon carried, but a weightstone applied to a weapon DOES modify attack speed - this is also a Vanilla mechanic for them. It's not worth doing for a cat set up but it is a cheap and effective consideration for bear form (as bears have a big fat slow swing speed that gets modded).
In Vanilla animal forms NEVER proc (or process) a carried weapon's special effect that is triggered by a random strike, such as a Fiery Weapon enchant or the stun effect from Unstoppable Force. Animal form attacks DO have the random chance to trigger worn items with the text "chance on melee hit" such as the Hand of Justice trinket.
As a general statement, one of the better enchants to get on a weapon for a druid for DPS is Superior Impact for +9 which is factored directly into your damage range. The enchant 2h weapon Agility for +25 would net you some adjusted attack power plus crit, but it falls short for total DPS added overall.
Druids in cat form can do some especially good DPS when they strive to get every Strength + Attack Power buff they can get their hands on, but realistically they will fall short of other true DPS classes by a substantial margin. How substantial? It varies from the classes, but a progression guild would be hurting themselves by having combat trinkets / jewelry / weapons go to a druid when a melee class would simply get a better return from them due to their class mechanics being built for it.
It's kind of like a Balance druid or an Elemental shaman gearing up for raid DPS and falling WAY short on effectiveness / efficiency in comparison with Mages & Warlocks if they had gotten the items instead. If your guild is great with it, cool.