While it is true that spell speed is the worst stat for a rdm,
I would like to remind that the contribution isn't 0.
Ss will reduce the gcd of all your spells which happen to be the majority of your dps.
The only actions not benefiting from SS are fleche and contre sixte, as well as your melee combo.

Everything else being a spell, they will benefit from it.
The only reason you don't want SS is because those melee combo +ogcd, while not being the majority of your dps, are still a significant part. So the stat doesn't affect a non negligible fraction of your output.

Spell speed will always boost your dmg, just less than other stats