Holmes and Moriarty were supposed to be on the same level intellectually, right? Moriarty had more resources in his criminal network, but they were basically intellectual equals. The Inquisitor and Solas are in no way equal. Solas can blink and turn people to stone. He created the Veil. The Inquisitor's unique power, the Anchor, is now gone. And even if they are the PC in the next game, they will necessarily have to start again at level one.
Trespasser made it clear that Solas knows how to manipulate the Inquisitor and the Inquisition, partly because of his trickster nature, and partly because he spent so much time getting to know the Inquisitor. The entire DLC was us playing into his plans. It also made clear that we need someone unknown to Solas to have any hope of stopping his plans.
Also, Sir ACD created Moriarty as a method of killing of Holmes, whom he had grown tired of writing. It wasn't until his audience's outcry that he continued to write more stories about him. And I've said before, Bioware is going to be very cautious about actually killing off a PC again in the future after ME3.
You're saying Inquisitor and Solas aren't equal mentally cus Solas manipulated them, but to be fair, Moriarty has managed to manipulate Holmes, too. That's why its an interesting rivalry; its theoretically possible for Holmes to lose. I'd say the Inquisitor has a good chance of meeting and besting Solas planning-wise now that they are onto him. The Inquisitor isn't written to be a fool, necessarily. You can *choose* to do stupid things, of course, but that's up to the player. The Inquisitor still has the potential to meet Solas head on, on equal footing.
That petrify magic of his that you cited might very well be able to be negated, for instance, thus putting them on more equal footing. It could be done through magical or mundane means, or even just psychologically in that Solas doesn't want to petrify his best friend/lover to death and can't bring himself to do it.
That last one is the most interesting aspect to me of the whole rivalry. Could Solas kill off the Inquisitor in a blink? Currently, I would assume yes. But will he? Can he actually bring himself to do it? If he can't, then why not and can that hesitation be used to reach him? Or can that hesitation be used to kill him, if that's your preference? That's where all the interesting story bits lie and that's something that, really, only the Inquisitor is capable of fishing out of his storyline.