For the Singularity Reactor, the biggest issue there isn’t going to be fixed by item level sync. The fight itself is tuned very low, and has always been that way, even when HW launched. I think the only way you could make it “more difficult” would be to adjust the tuning of the fight itself, alongside an item level sync. Currently, even minimum item level, no Echo, and even going so far as to remove pieces of gear for a truer sync, Thordan falls over. I remember doing it in HW with a mixture of i130 ironworks, Vault, and Gubal gear and he couldn’t even kill me (I was a BRD and messed up a lot of mechanics, but never died; I remember this vividly).

I agree that all of these should have item level syncs in them. Even the Alliance raids could stand to have item level syncs, because it’s astounding how quickly you can rofl-stomp them when the next tier of gear comes out. The only one that manages to retain any semblance of at-release difficulty is the third one in the series. (With the exception of Orbonne, which was neutered by the added Echo and nerfs to TGC. )