Actually, Serk was pretty savvy with magic.
He hired Scarlatti not only because he was an excellent duellist, but also because his sword hindered magical healing - so, when Scarlatti 'disarmed' Donovan, there'd be no way that Donovan would be able to play for any concert.
He also had a 'pocket house'. "Very powerful magic. Very expensive."
Provided what Barnet said was true, and this isn't another lame red herring, he also knew enough to use a go-between to hire an assassin and specifically point her to an ex-blinder in order to get the gear...