I cannot see the armory, as you have stated it is under maintenance, so I'll try my best to answer your questions.
1. My personal preference is to hit the keys lightly, but it all comes down to preference. As long as it doesn't tale you two seconds to switch from shield slam to revenge.
2. You are facing what many warriors have been dealing with for a long time. Lucky for you, the end of that is now in sight. When dealing with a multimob group, all you can do is shout, clap, tab devastate, cleave, and pray. There are ways to help make it easier though.
3. How is your threat set? How much hit and expertise do you have? How much strength? How overgeared are the DPS?
4. Is it just specific fights where you have problems in threat, or is it all the time?