I'm of the opinion that xenon should not be able to wear this gear.
Why you ask?
At seven stars, the pieces will all have around 165 all stats.
Xenon has three main stats
165x3 = an effective 495 main stat from each equip
three pieces in the tyrant set means 1,485 bonus stats (AND THAT'S BEFORE POTENTIAL)
Let's assume that you get a measly 6% all stats on each piece, and add a 2% neb.
So 8% all stats per piece for 24% all stats.
Which comes out to be around 368.2 levels worth of AP.
And that's just from the stats that THOSE THREE PIECES ADD, AT A REASONABLE ENHANCEMENT LEVEL WITH A FAIRLY COMMON POTENTIAL LINE
A xenon equipping the seven starred triple set tyrant threat at level 150 will become effectively 297 levels worth of stats stronger, and that's before potential.
If you have thief or pirate tyrant gear... there's honestly no reason to play any other thief or pirate if damage is what you're interested in.