You definitely want to start key binding your abilities now. Get used to it now because you will get a lot of abilities that you will use on a regular basis. If you do not have a mouse with programmable buttons implement "alt+(insert button here)" along with shift. For abilities that you use more often, set the key bind to something easily accessible. For instance I have ravage on R, choke/stasis on G, etc.
And lastly try your best not to tunnel vision on one person. You will always be up in someones face trying to burst them down. Make sure you are aware of your surroundings the best you can. For instance, something simple like positioning yourself between a sniper and the pillar in Void Star.