Deidara is UNDERRATED, his nano bombs is almost a guaranteed ko to anyone without dojutsu, or is a potent sensor, secondly he trained himself to see through genjutsu, this is something that ppl seem to be blind to the value of. He saw through a regular genjutsu, which is far more faster than breaking it the normal way, which is done by disrupting chakra.
Furthermore his taijutsu isn't too shabby, nothing to write home about, but he did fend off kakashi and gais teams with NO arms. Last but not least, he managed to use a few jutsus without even having arms, like when he substituted a clay clone when naruto was beating him, and again when he used a suicide clone, that nearly killed everyone were it not for kamui. all in all I'd say he's fairly underrated, he has enough power to bomb entire villages and plenty of variety with his clay creations, his versatility and power is off the charts