I'm on my first playthrough and I was keeping my eye out for a weapon that might synergize with a Shifter (who will not even have the weapon equipped for most of each fight). I think I've found it in Scordeo's Trophy. The idea is to get some stacks of Strategic Blitz* (SB) up before spiritshifting and enjoying significantly reduced recovery for your melee attacks for the duration of the shift (and a good chunk of the next one).
Ranger multiclass is perfect for this because their fantastic accuracy bonuses can allow you to effectively use the pistol modal, which cuts pistol recovery in half at the cost of accuracy. This allows you to stack SB very quickly. You also get the fantastic Evasive Roll (ER) ability to close distance + shift + attack with bonus dexterity instantly. It also helps that firearm reloads can be canceled unlike other recovery phases.
Spiritshift armor has no recovery penalty, and spiritshift weapons are dual-wielded. With SB stacked on top, you can achieve very low recovery times. With high INT (which you should have as a Druid), you can have the buff last nearly two shift durations (easily over 40s). It's almost like turning INT into DEX. By using ER or CC, you can break engagement, re-apply the buff, and shift again. This has a significant impact on spiritshift DPS and gives you something to do other than auto attack.
In a nutshell, ER, Ranger accuracy, the pistol modal, capitalizing on INT, spiritshift speed, weapons, and armor, all come together to make this the perfect weapon for the Beastmaster class. Just be sure not to get too far from your companion when shooting if you're using the Stalker subclass (which you should be, with Shifter).
Sorry I don't have more hard numbers, but I think this is neat and wanted to share.
* I thought hard about using Opening Barrage because it can also help with casting and shooting, which can become important in long, tough fights. But ultimately you spend so much more time shifted than casting that SB is the superior choice. Might be interesting to try that out with a Ranger/caster.