Yamamoto did not beat Senna once, fact. Senna outqualified Chandhok 6-3 and would of slaughtered him in race head to heads if he had not suffered atrocious reliabilty, when they both finished a race Chandhok only beat Senna once. Senna has not been given a chance yet in F1, that HRT does not count because not even his uncle could look good in it, especially seeing as it was even slower than the other HRT. Senna deserves a chance because he was very unlucky not to get the Honda 2009 seat after impressing Ross Brawn after his test and it was only the fact that Honda pulled out of F1 that prevented him getting it. He has beaten drivers such as Maldonado, Buemi, Petrov, d'Ambrosio and Kobayashi in GP2 who are now all in F1, so why should Senna not be given a chance?
Senna beat all his team mates and it was only his catastrophic reliabilty that prevented him from destroying them. In the entire season Senna had 9 DNFs, 1 was a driver error in Barcelona where he got a bit carried away after having an excellent start, another one was at Singapore after Kobayashi crashed on the racing line and the marshalls were not quick enough with the yellow flags and Senna coming around the blind corner could do nothing to avoid the crashed car, the other 7 DNFs were down to mechanical failures. Senna's average grid position was 22.3 and his average finishing position was 17.4 which is a climb of 4.9 which I think is very good. He was also the only HRT driver to outqualify a different team car in normal conditions. It is also worth noting that Senna outqualified Chandhok at Monaco while driving a damaged chassis.