Hey dude, here's a couple ideas for you to consider.
Before you start modding or completely rearranging your rig, it would be wise to make a bit of a study first. Find some different guitars, rehearse them and compare to yours through your amp and your cab at all volume levels. Try at least one different speaker cabinet. The cab's role in determining the spectral balance of your tone is critical.
Once you do a little test like that, you'll know whether the issue lies in your amp, your cab, your guitar or all three and to what degree.
Having tried a couple of 2204s, I don't find them "extremely bright" personally. They do have that upper mid brilliance that has Marshall written all over it, but it has never been obnoxious to my ears. These amps don't have a reputation for consistency, so two examples sounding a bit different from each other is a natural thing. However, each and every one I tried sounded gutsy and familiar. Cranked to about 7-8 on the master dial, they all delivered that nice oomph through my 4x12 w/ some old Vintage 30s. I hate to say that, but maybe your amp needs a service?
Listen to the guitars unplugged as well. If yours are way bright naturally, see if you can find suitable Graphtech saddles for your bridge. They do a wonderful job taming excessively zingy guitars.
Get a handful of picks. Shoot for 1-3 millimeters thickness and a smooth feeling surface. Avoid unusually sharp tips and hard materials. It might be uncomfortable at first but won't hurt you. It costs a bit of patience but few dollars.
Then think about your pickups. The Full Shred and the Screamin Demon are great but perhaps just not the most fortunate choice for your application. You might be better off using something like the Invader or the PATB2. The Alnico 8 mafia might be able to help you, too.
I'll generalize a bit saying that Dimarzios typically tend to have a somewhat less present high end, compared to Duncans. A Tone Zone or a Super Distortion, for example, might work for you.
And last but not least: take a look into active pickups. Don't bother telling me how much you hate the idea. Personally, I am not a big fan of those in a general sense but I assure you they can be positively devastating in all-maple guitars.
