~50% CPU Usage by Ionic CLI

I recently noticed that my MacBook becomes really hot while working on an Ionic project. The project isn’t that large, but I’ve been working on it for several weeks now. While the Ionic CLI is serving a project, its CPU usage is usually 50% or more.

I also noticed that whenever I start ionic serve, I get the output

Gulp startup tasks: [ 'sass', 'watchTypeScript', 'watchSass' ]

and then it takes more than 10s for the next lines to be printed, which is

[13:00:59] Starting 'sass'...

I don’t know what I did (I updated to the latest OS X 10.10.2 beta), but this delay suddenly occurred, instead of growing overtime. Might OS X be the reason?
Is there any log I could look at for further information about what’s taking so long?

Edit: Screnshot of the processes, sorted by CPU:

Edit #2: By shrinking the scope of the watchPatterns in my Ionic.project I could determine that some included /lib subfolder must have been the reason. I altered my watchPatterns and it’s working beautifully now:

"watchPatterns": [ "www/**/*", "!www/lib/**/*", <--- exclude all files in /lib and its subfolders, "www/lib/Services/**/*" <--- ...except my own services ]