Increasing the refresh has not been necessary for anyone to date, but if you wanted to try it you could certainly ask The Vicidial Group to double the refresh rate in a screen for you (or create a refresh rate preference so you could play with it). Consider creating a ticket in the "Issue Tracker" (Link at the top of the screen) and seriously consider sponsoring it. If your mysql server, agent workstations, and network can handle the load.
Advice given to all clients in our colo and in general: THREE carriers minimum. Paychecks ride on this, there is no excuse for "oops, the carrier is down so you can't feed your kids today, sorry". LOL
Seriously: All carrier's go down eventually. Maybe only for 20 minutes ... but when you're IN that 20 minutes you do not know how long it will be. So ... do you send everyone home? After 10 minutes? 30? An hour? Hm. Change an 8 to a 9 and *poof* another carrier goes live and quite often the agents never even know it happened.