I think this 'sensible batting' is the root of the problem. Management/captain etc. want the top 4 to 'make big scores'. That includes Warner, but it seems to mess up his mindset more than anything. I think in time Warner will work it out, and he's already shown a few signs in the IPL thus far of being more measured, but still effective. I'm hoping that with Watson back at the top, Warner will feel less pressure for a big score and feel more free to attack.
Looking up some stats...the Warner/Watson partnership hasn't been too productive thus far in ODIs (26.45 partnership average in 11 opening stands, 4.40 RPO), but then again Warner hasn't really had productive opening stands with anyone:
with Wade: 14 inns, 36.71 avg, 4.99RPO
with S.Marsh: 5 inns, 34.00 avg, 5.12RPO
with Ponting: 3 inns, 23.00 avg, 7.01RPO
with Hughes/Clarke/D.Hussey: 4 inns, 14.00 avg, 3.61RPO
In fact I can only find 5 50+ opening partnerships featuring David Warner (3 with Wade, 1 each with Watson and Marsh), pretty low for a guy who's opened 37 times. Statguru tells me there have been 330 50+ opening stands in the last 5 years out of 1265 completed opening partnerships (1 every 3.83 innings). Going by that, Warner should have featured in 9-10 50+ opening stands by now... so it's fairly safe to say that the Aussie opening pair has been a problem, and needs to be fixed. Not all Warner's fault of course, but I think he's got a fair bit to answer for.