no doubt its a combination of many things, but is this really a rules/car dimension/track design issue rather then an issue concerning the relative performance/speed difference of the teams?
hence why most of the passes we saw this year occurred when a faster car was hamstrung by penalties which put them outside of the natural running order.
this has been a problem for a while now...which is shy they brought in DRS in the first place. to encourage close racing and passes by trying to (artificially) eliminate the performance gap between teams.
maybe a budget cap wont get rid of this problem (not because it cant be enforced but rather because some teams will always be better at spending a fixed amount of money then others) but we have seen different car designs, different tire constructions, different track layouts and the problem yet persists.