The problem is that the DirecTV dish will not be designed to reflect signal back to the same point as what the Dish network dish is. I installed Dish for 5 years and can tell you that the shape of the dish is extremely important. I have been to houses where the signal is weak and no matter how much tweaking to the aim of the dish I did I could not get signals right. Grab a new pan and install it an signals would jump back to normal. I could put the old pan over the top of the new one and barely tell the difference in shape.

Eastern Arc like what you have (depending on where you live) the signal levels can be much lower than Western Arc. In my area we have the ability to install either Eastern or Western depending on obstructions. Western Arc signals would vary between mid to high 50s on sat 129 to high 80s low 90s (on a really good day) on sat 119. Our Eastern Arc signals were between mid 30s to low 50s, and every once in a while you get the perfect LNBF and pan and hit a mid 60 level.