I was reading the Canticle of Shartan again in WoT2 since Divine Leliana at least has now restored it to the Chant. I think there is a certain significance that during the game we found codices that essentially contradicted the history of Andraste as contained in the Chant. Now it is suggested that the Canticle of Shartan may also bear little resemblance to the true historical figure. In fact it was only written down on the instructions of the first Divine and had only existed as an oral tradition among the elves up to then.
So my theory now is that these hints linking Solas to Shartan are to alert us to the fact that whilst Shartan was an historical figure, the Canticle itself may not actually be about him. If you go back to the history of Shartan as related by Sister Petrine, she states that Andraste's victory at the Valarian Fields might have not occurred had it not been for a "rebellion behind enemy lines". It was previously suggested that Shartan was the commander of a slave division in the Imperial army. Now the army would have been commanded by mages and they normally do so from the rear to keep clear of threats while they hit the enemy with spells. If their slave guard suddenly turned on them, that would have been sufficient to turn the tide of battle.
I suspect that Shartan was familiar with the old elven folk tale about the trickster warrior who aided the enemies of the tyrants who ruled them and he used this tale to encourage his followers to pursue his proposed action on the eve of battle. Over time, when elves passed the story of Shartan down the years, the two tales became combined into one and that is how it came to be heard by Chantry scribes who noted it down for the Divine.
If you look at the Canticle of Shartan and substitute the names of Solas for Shartan, Mythal for Andraste and evanuris for Magister, it could definitely be telling the story of Fen'Harel's rebellion. In it the elven slaves flee into the wilderness away from their masters, pursued by hunters (servants of Andruil?). They start to doubt their actions and wonder if they might not be better off going back and throwing themselves on the mercy of the evanuris. At this point Solas appears and argues against this, pointing out the evanuris will just use them as an example to other slaves of what happens to those that rebel. Instead he encourages them to fight for their freedom. He enables them to outwit their pursuers by using guerrilla tactics, falling upon them and slaughtering them all. In WoT2 there is an illustration of this but instead of showing elves and humans (as you would expect), it shows wolves bringing down a stylised deer. Symbolic of Fen'Harel's followers falling on either Andruil's or Gil'naan's. It would certainly suggest that it was this incident that caused the evanuris to dub Solas the Dread Wolf.
Then comes the next bit which is meant to recount the meeting between Shartan and Andraste but I feel now is more likely recalling Fen'Harel and Mythal. The elves hear and see another great army approaching. Fen'Harel tells them he will investigate who they are rather than risk losing all his followers. He sneaks into camp, is captured and taken before their leader, a "Lady radiant and clad in armour of bright steel", surrounded by her followers, many of whom bear the marks of slavery. She declares that "All souls who take up the sword against Tevinter/Evanuris are welcome here". Then Mythal invites his followers to join her.
Their combined forces advance on Minrathous/Arlathan. In the subsequent battle it is the actions of Fen'Harel that prevent Mythal being cut off and overwhelmed by the enemy. With the battle won, she proclaims "Behold our Champion" and gives him a weapon that her mother once possessed, telling him "Take this, my Champion, and free our people forever." Odd word that "forever" from one mortal to another but not to one near immortal to another. Could the weapon she gives him be not the sword in the current version but actually an orb of power? The depiction of the Dread Wolf guarding Mythal certainly would fit with him being her Champion. Then the Canticle ends with them standing before the gates of Minrathous/Arlathan ready to make their final push against the tyrants.
What follows in the Chant is the story of Maferath's betrayal through jealousy of the Maker and in fact Andraste herself, whereas the historical account clearly indicates this was likely a strategic decision on his part. So could the betrayal contained in the Chant bear more relation to the betrayal of Mythal than the historical Andraste? Whatever the case, I'm definitely inclined to think that the Canticle of Shartan does contain far more of the story of Fen'Harel as contained in the ancient elven folk tale passed down among the slaves than the actual events that surrounded the historical elf of that name.