I don't think it does affect. However, I tested if gear affects flash and it does, I tested it with a pld friend his ilvl gear was about ~70 and I was 80~90, but the difference wasn't that huge.
The test went like this: I flashed (hate on me) > he flashed (hate on him) > I flashed (hate on me)> until the 4th-5th round, he flashed yet the mob was still on me. Of course the test was conducted with the use of flash ONLY (shield/sword oathes were not used).
off-topic: only use flash for a group of mobs, if it's only 1 mob it's better to spam the 3 WS combo.
EDIT: duh obviously gear will affect flash, since magic damage of my sword was higher and flash is magic lol XP.