The $0.40 cost per day I calculated includes multi-AZ HA, and your bursts would have to be fairly significant to overwhelm two t2 instances which are accumulating CPU credits 95% of the time - say around 600 requests per minute for a few hours.

Of course, this is all conjecture since I can't actually view your workloads, but we've been performing this exercise for our own services, and the t2 series of servers is remarkably capable: especially given their cost. The original administrators thought (or were lead to believe) that we really needed the raw horsepower that c*.large+ instances offer... and they didn't in most cases.

Routers, crud API wrappers, even some disk persistance applications all qualify as "non-CPU intensive".