Here is a video of me killing Ionat solo, for Shamans interested in soloing 6+ Dragons.
https://www.youtube.com/watch?v=oPxeOVuX0G8
This video's strategy would apply to killing Ayillish as well, but she was not up at the time. Please note that this was only doable because Entariz was dead or pulled away at the time (not sure which). Normally Entariz will always social agro with Ionat (unless you got help from someone like a Druid). You probably could find a way to get one of the two solo if both are up, maybe rooting/snaring and either camping the agro or attempting to leash the Dragon you do not want. This would be a very high risk strategy solo, due to things like adds and resists to root/snare, but I think it is possible.
Therefore, this specific video shows more of an "attack of opportunity" against Ionat if you happen to see him up alone. You could try Entariz in the same way if Ionat is down, but I haven't attempted that yet. I am afraid of Sont agro, so it would probably only be doable when Sont is dead or pulled away. Entariz should be soloable just like Ionat, since Entariz does not CH or gate.