Centaur 1

The washer has nothing to do with fixing any wobble, they put a washer there to hold the blades in place while screwing the head into your arrow. The washers are also made from steel so that the blades won't damage you inserts upon impact. The slick tricks are inherently accurate because they area a one piece head that is machined to tight tolerances from hardened steel. If they wobble there is a problem with your arrow or the insert not being installed straight. A lot of things can cause this, the arrow saw might not be perfectly square, or whoever installed the insert might have left a small burr in the arrow. These sort of errors are harder to spot with field points because they are short, the extra length of a broadhead will compound the error.
When a head is screwed into an arrow the head is alligned with the shaft by the straight portion of theshank that is above the threads. They hold a very tight tolerance on this straight section so as to keep any slop between the arrow and head to a minimum. (A little trick is to coat the threads and the shank of a broadhead with string wax. What little play there might be is removed by the heavy wax. It also helps keep the head from working loose.) If that straight shank was not there on a broadhead, the wobble wouldbe horrific. You see for a thread to work without binding and galling, there has to be clearances built into the threads. This clearance would create all sorts of variable to be induced into the equation.
Now onto your Muzzy's. Keep thinking about what I said concerning the slop between the threads. You received your Muzzies from a friend so I'm going to assume that you personnally did not assemble them. The bad thing with a Muzzy is that the blades are held into the ferrule with their "trocar" tip. When the ferrule is machined the threads for the tip are cut on the front end of the ferrule then the slots for the blades are cut into the tip. If you know anyone who is a machinist ask them what happens when you take an aluminum shaft thats the diameter of an arrow, then starting at the end slice longitudinal slots into it. Depending on whether you have 3 or 4 blade heads, you'll be left with 3 or 4 fingers of aluminum that have a tendency to bend outward and maybe even twist. This is the fun part if your still reading this far into my post, Now keeping in mind that using threads for alignment is inaccurate, and that the ferule now has a slight bend and twist from themachining process; at this point on a Muzzy broadhead you will insert the blades into the slots and screw the trocar tip onto the end, using the threads to attempt realignmentof the four fingers of the ferule, the four blades, and the tip itself. Sometimes it works and sometimes it doesn't. I've personnally checked this using a granite surface plate, vee blocks and a dial indicator. Even when I use this setup to try and achieve better arrow flight, I only get patterns which could be considered "good enough".
Now about Slick Tricks, there's no such alignment problems, the ferrule is solid steel, without that extra tip that screws on. Everytime that I've spun an arrow with a Slick Trick installed, it has spun perfectly. And yes, I use the same dial indicator on them also.