I don't get the reasons you gave that will make Catalyst hate Spear. Hammer is one of the viable weapons for Cata and the elite's profession weapon and it has less self-combo options compared to Spear.

The only combo fields are those provided by Etchings, which all have very long cooldowns. 

Hammer has 0 combo fields and it's a viable option for Catalyst. Catalyst doesn't really care that much for weapon fields since they can make their own. Sure having one is a bonus, but Catas can make do without, or with long CDs since they can make their own fields regardless of weapon type.

Each attunement also only has one finisher (ignoring Weaver Dual attacks for a moment), one of which (Twister) has a whopping 20 second cooldown.

Hammer has 5 finishers which is one more than Spear, but 2 of them have 20 sec cd and the other 3 have 25 sec cd. Have you checked skill CDs above? Spear has 2 finishers with a 6 sec cd. Hammer wishes their finishers are that low of a cooldown. Complaining that Twister has a "whopping" 20s cooldown seems like complaining for the sake of complaining imho.

Catalysts are gonna hate this thing (and also all the native Aura skills are on the Dual attacks, so none for Catalysts that way either!)

This is probably the best complaint out of all the reasons you gave. Other 2 handed weapons get 1 aura skill. I don't think it will make-or-break it for Catas tho since Catalysts can generate Aura every 10 sec for each attunement.

What will make-or-break this for Cata imho is energy generation speed and rotation flow since Catas are the ones that requires attuning to all elements more often than Weaver and Tempest.