"I sometimes try to leg into strangles like you did, but often find that unless you're spot on with your timing then you get just as good a price opening the spread in one go."
If you think about it, shorting one leg of a two leg spread and waiting for underlying movement in order to short the other leg at a better price, is exactly the same as..... going long one single leg. In both cases, underlying movement must overcome option time decay for you to be better off.
Some you win, some you don't, about 50-50 in my experience.