As others have said, looking cool and having fun is all good and dandy, but the majority of the FFXI player base won't give a SAM/DRK the time of day simply because there are more effective combinations. While the lack of freedom to experiment with subjobs is often disappointing, people want everyone to function in a party to the absolute best of their ability. That means having the subjob that best compliments your main job.

We're not joking when we say that you'll have trouble progressing in the game as a SAM/DRK. If you want to use fun subjobs, it's best to do it when you're playing solo. Otherwise, you won't get very far.