RDM with 343 @ 5k DPS? NEVER EVER!!! Even 99% percentile in fflogs is below 5k.

Have a look at fflogs with 75 percentile to get a clue where you should be: https://www.fflogs.com/statistics/17#aggregate=amount

75 percentile is at 4,3k DPS for last 2 week.

With your gear you might be somewhere around 4,5k but not at 5k.