Wondering how good this buff is really. 

It stacks with Frenzy and Bloodlust and other attack speed buffs if that is what you ask. You can see the effects of it when you hover over your weapon's tooltip's recovery number. Since it's working for everybody in an AoE it's pretty good.

 

There is no additive/multiplicative distinction with speed bonuses in Deadfire as there was in PoE afaik. Under the hood they all work the same (some influence attack animation and recovery, some only recovery). The Ward gives you a bonus to animation speed as well as recovery.