you are right about the fact Timefactor should be used in an FX loop if you want to use the amp distortion.
There are a few factors to consider:
-the Eventide pedals are true Line Level devices.
-make sure you know which type of level your fx loop uses (-20/-10dB or +4dB)
-amps may use different level controls to feed the FX loop. Most use the Master output as Send control. Others have a dedicated SEND knob, mostly on the rear panel, close to the loop. Some may use the preamp gain. You need to understand how your amp works in this regards and use levels accordingly. Not all fx loops are created in the same way and some are also poorly designed.
all the best