Mirage banner is okay but has a pretty narrow application -you're probably best off avoiding that one for now and stick with BotUL, War banner and IotSE.
I think you've misread the entry for IotSE. Simply put, it just gives you +1 to hit on the first round of combat. It does not grant any extra attacks at all.
As for the question about match ups...
Elves comes in three delicious flavours of course and much depends on wich one you're up against. Poor old wood elves are easy meat for us (and seemingly everyone else come to that), high and dark elves can be problematic if you don't have a good list or know how to handle them properly. For the most part we can give any elven army a really good game because our shooting is so formidable against their low toughness and typically low armour. The trick is to shoot at what your archers will be most effective against -NOT what scares you the most.
Dwarves used to be another pretty good match up for us but they have been bolstered significantly by the 8th edition ruleset. On the face of it our armies are completely different but when you look at them a bit closer you'll see they actally work in a very similar way by leveraging their high CR. They have an edge in combat but this is offset by our stellar magic phase wich will typically mean we can out maneuver them. For this reason the stunties can give you problems if you go in recklessly with all guns blazing and expect to win -you wont. For most lists your best bet with these is to stand off them and break them down with ranged attacks (most notably the SSC) before you even attempt to try and tackle them in close combat. It's a tricky match up and much will depend on the exact lists used and the relative strength of the generals.
Generally speaking we can outshoot anybody and opponents who field gunlines against us are in for a tough time of it.