Obviously this includes the Ashes whitewash, when everyone did bad, but even taking that out he only gets up to 36 since then.
Thing is, he gets a 50 or ton often enough to keep the questions away from him, and the 2013 summer Ashes, probably his best, seems recent enough. But he has fallen off a cliff since then, and as he and Cook are the two most experience batsmen & should be doing most heavy scoring but he just isn't up to it.
It depends upon that great conundrum of English cricket : is Ian Bell really world class, or does he just look world class?
Before the Ashes 13 series, I would have said the evidence suggested he was often style over substance, but then he reeled off those match winning knocks and for a little while looked like he'd finally turned into the player everyone was hoping he'd be when he first arrived in the game.
Now it's been long enough since that burst of consistent form that you wonder if it was just an isolated peak, and with the 2015 Aussie attack surely far more potent than in 2013, and the English batting wickets almost invariably fiddlier to bat on than Australian ones, whether that spell of heroics is really much of a guide to likely future form.
I'm kind of agnostic at present. Of Root / Bell / Ballance, Ballance unquestionably looks like the guy who is going to struggle the most technically with extreme pace and movement, and Bell is certainly better equipped in this department. Against lesser bowling attacks recent form suggests Ballance is the more likely to make big scores, but he's not looking like a great bet against pacey swing bowling in English conditions at present.
Which is not to say I'd actually drop Ballance if I were a selector. The guy has earned the right to prove whether his technique is up to it. But that's why it's so important to pick the right batsmen against the lesser attacks, because the number of potential picks capable of succeeding under those conditions is necessarily much greater than the number who can also succeed against the best attacks.
EDIT - although now I think about it there is an obvious counterpoint : Bell is probably technically capable of nicking deliveries that Ballance would miss.