Looks to me that if only the top 2 strings are higher that the gauge of the strings are to thick to slip into the nut slot or that they aren't in the slot at all but just on top of the nut.

As for Elixirs, they are more expensive but they last very long but like you say, the sound isn't that great. Always loved D'Adarios on my electrics and Martin strings on my acoustic.

Herman