Nice job, from 2,3 MH/s to 2,5 MH/s at my R9 280x GPUs

Continue improvements buddy

Change your command line from --kernel jackpotcoin to
--kernel jpc and get something between 3.5mh/s to 4.2mh/s instead

...and also get the 14.6 drivers like djm34 suggests as well!
Man, I'm not an idiot, I've changed the kernel. It's only
R9 280X not
290XI didn't misread, I know you have a 280x card. The speed range I quoted are roughly what you should be getting, even if you have not overclocked your card.
Here's 4 x 280x cards at I:20...

You should be getting at least 3.5mh/s with your lower intensity setting.