The VariX 3 should be just fine at 2X for poor-light conditions. All you have to do is to try it out in the light conditions you are questioning. Afterall, you're the one using it.
: Other scopes for this are the Bushnel Elite 3200 or 4200 in low powers. They are usually brighter yet than the Leupolds and are actually tested on a .375H&H.
: I've never had trouble with either on heavy kickers. My present .375 has a straight power 2X Leuopold which is also perfect for large calibres for big game shooting.