Your use case could be based on simplified architecture by using ST as the main controller instead of relying on many hubs and integration components: ST, IFTTT, wemo, and Nest/Ecobee.
I’d recommend to use another energy monitoring switch (such as Aeon smart energy: they are cheaper than Wemo and can be connected directly to ST).
BTW, I don’t own any wemo switches, but based on some feedback in the community,it seems that Wemo switches are not always responsive.
see Belkin WeMo Compatibility with SmartThings
By simplifying your overall architecture, you’d probably have better response times and be less sensitive to outages.
Regards.