If you don't have a reputation in the DAO, what kind of protection do you get in case such stranger wants to rip you off? Sure, he might look trustworthy, according to the offer table, but can you risk trading without Bisq?
The point I'm making is that by this point it isn't a stranger. Without revealing too much for my own privacy reasons, there is another party I first met through a DEX and whom I have traded with probably 100+ times over many years, both in person and electronically. There comes a point where you have enough mutual trust to start trading small amounts without using the DEX and/or escrow, and then building from there. Obviously I would never suggest going off-DEX with a stranger.
Do want to trade likewise to avoid the DAO fee?
It was convenience rather than fees, but no one is going to say no to paying lower fees in any situation.
Can you become part of the DAO somehow, and set your own fee as arbitrator? Competition is what would lower the prices, and I'm sure part of high trade fees is small number of arbitrators.
I'm not sure if I'm misunderstanding you, but Bisq arbitrators do not set the fees, they simply moderate any disputes.