Boss Tricks: Trace
Upon encountering Trace in Sic Transit, perform a charged Missile Jump (at the same place used to scan the Sic Transit spectral locks more quickly) to access the platform from which he is sniping you, which will cause Trace to stay up there and be relatively still. Then, use the Shock Coil to take him down quickly.
Note that Trace does not alt-form when using this trick, so it is not as effective if you are going for 100% scans. You can still use this to lower his life quickly, then drop back down from the platform to cause Trace to behave normally.