Wardens are, in fact, capable of throwing attacks significantly more powerful than a plasma howitzer. Real Howitzers are are only Weapon: 6 or so, Plasma ones maybe Weapon: 8. A full Warden? Weapon: 11 or 12 with Fate Points.
And Jedi precognition is in no way capable of warning them whenever they cut their hair, because someone might be grabbing it for Thaumaturgy. If it were that good, they'd never get surprised by anything, and they clearly can be. It's almost always split-second precognition, not long-term. Thaumaturgy is the definition of long-term.
Or there's the possibility of attacks that aren't helped by seeing them coming, suvch as raising the internal temperature of the Jedi's body with raw will until they pass out. Seeing that one coming doesn't really help.
Andd finally, what about the behavior of the Wardens leads you to believe they're incapable of being tactically innovative? Ramirez's combat prowess and style? Morgan's use of nuclear weapons? They're somewhat conservative politically, but that's not the same thing as being incapable of creativity.
I'll admit that Wardens would likely lose in hand-to-hand, but a Warden with any brains at all wouldn't be in hand-to-hand.
Now in terms of specific characters, I'll admit you probably need a Senior Council member to take on Yoda, but most of the rest? No match for a Warden with prep-time (though they could probably take an unprepared one).
