It's amazing what happens when you pick someone for test cricket based on their red ball ability, than on their white ball ability.
Roy and Buttler have done nothing at domestic level in red ball cricket (albeit not that Buttler gets much of a chance, to be fair to him). Whereas Burns has, as you say, being dominating county attacks for years now. And look at the difference.
Even Denly you could argue is being picked because of his white ball form (but at domestic level, not international level). He was a huge asset as an allrounder for Kent last season in white ball cricket, and it was arguably that spin option which saw him go to SL over the winter - and almost accidentally stay in the test team thereafter. (We do like to take a county batter who bowls some spin to test matches in Asia: Samit then Ansari then Dawson then Denly all in the last few years.)
Buttler batting at seven, not keeping and not bowling. I wouldn't be that to a child of mine in test cricket. He has no right being in the side and batting below six in my humble opinion. Denly, Roy and Buttler have never been able to hack it in county champ div 1. I'm realistic about the returns I want from everyone in the side. Opening the batting or batting 3 is extremely hard, everyone else is having the times of their lives are 4,5,6 and 7 as specialist batsmen. Being a specialist batter and batting below 6 - shouldn't be a thing. I suppose finding an opener to compliment Burns is deadly difficult, he is a very self confident player. Boycott would have been a good foil for him.
I agree about Roy, Buttler and Denly. They were all picked for their white ball form which I don't like. Denly is a poor bowler for this level.