They don't lose those things. During Broken Circle, the Tranquil in charge of the store room will refuse to leave it, even if you order him to, because he thinks he is safer if he stays where he is. He clearly still has survival instincts. He's not going to go running through floors full of demons and abominations if he doesn't think he has another option. And in Inquisition we hear from more then one Tranquil motivated to find places and ways to apply their (sometimes considerable) knowledge and live useful lives, even in a world that can't help but be freaked out by them.
Yes they do. Lobsel has already addressed Owain. Tranquils do have intelligence to reach logical (even if that logic is rigid flaws, like in case of Owain) conclusion, or have rudimentary flashes of own desires, but that's about it. After all, didn't you find it odd that we only find ONE Tranquil in Redcliffe left alone by Venatori? Heck, we know what happens with the rest - murdered to make Oculara. None of them had protested when Venatori were ripping skulls out of their heads.
Then there's Minaeve who not only spent a lot of time with them in teh CIrcle, but protected them during time of rebellion. She tells Inquisitor that they practically have no emotions, can barely take care of themselves ans have no eans to defend themselves and won't protest or do anything if someone mistreats or hurts them.
When we meet Helisma, she tells us that she researches animals because Minaeve told her so. She only vaguely recalls that she used to like animals. She hardly even remembers what exactly led to her Tranquility. That's a common theme among Tranquil - they hardly remember their past lives or past personalities. They are as close to meat automatons as you can get - someone issues a command and they act. If someone does they get lost and only do basic things, search for someone to give them command (Minaeve, Inquisitor, Samson) or continue with their past assigned duties, like Owain taking care of store room.
The Tranquil may not express themselves the way they used to, but they still possess the things that are supposed to be taken from them. And, again, we don't know if these things are specifically linked to the Fade, or if they are just how the Fade pushes through to affect our world. Chicken/egg.
If you say that these things are 'chicken/egg' you basically agree with me that these things are irrevocably interconnected 
Tranquility cuts away something, but whether that something is really related to the Fade itself or if it's a sort of lobotomy that represses the things that a mage usually uses to control the Fade remains to be seen.
I'd be curious to know what happens if the Rite is performed on a non-Mage. There's a lot we don't know about Cassandra's vigil, but THAT doesn't involve lyrium, and the Rite does. Again, getting lyrium branded into your head doesn't sound healthy under any circumstances, but is that what makes Tranquil so... tranquil? Because if so, then the Rite just takes your desires and dreams from you, and doesn't really affect your connection to the Fade at all.
We DO KNOW what happens if the Rite is performed on a non-mage. I've already mentioned that not so long ago. All future Seekers go through Rite of Tranquility and some of them fail and stay Tranquil. In fact, the first Tranquils we know of were in fact non-mages.
From: http://dragonage.wik..._of_Tranquility
"We called it the Rite of Tranquility: a mind, branded with lyrium, brought to a state devoid of either emotion or sense of self. The rite was required to achieve the true peace that could draw a spirit of faith from the depths of the Fade. A difficult task, considering a Tranquil mind is all but invisible to these beings. The candidate must be pure. If the candidate proved worthy, the spirit would touch his mind... and he would be freed from Tranquility as well as made into a Seeker in truth. If he proved unworthy, Tranquility was permanent.
It was only later, when the first mage attempted to join our Order and failed, that we learned Tranquility rendered a mage unable to access his magic, as well as immune to demonic possession. Thus, when the Circle of Magi was born, we gave them the most holy rite we possessed. It was a sacrifice we made for the good of all, so dangerous mages could be spared execution and yet live productive and harmonious lives. What we did not give them was the secret of its reversal. That knowledge, and our ancient bond with the spirits of faith, shall forever be solely ours to keep."
ot saying the Fade doesn't sound like a great thing to have. Just saying it's a leap from that to the assumption that losing access to the Fade forever would result in everyone being made into vegetables. Life seems to continue on, Fade or no fade, and the Tranqulity only comes into it as as we mortals fumble to control how and when it gets used.
Not saying it's impossible that it would make everyone vegetables, mind, just that we can't treat it as an automatic thing. As I've said, I wouldn't put it past Bioware to make "must destroy all magic forever" the Dragon Age version of ME3's "must destroy the mass relays," ending choices. Here's hoping they handle this one better, if it comes to that.
Life seems to continue only because most people haven't been cut from the Fade entirely. Most still retain some sort of connection. And we do know that Tranquil hardly ever survive on their own.
Then there's Cole, who tells us that not only Fade is still around modern Thedosians, merely altered (because of the Veil) and that without minds of living spirits have nothing.
"It is here but held, constrained by a construct, Veiled. Feelings, memories, minds, mortality: all shape it, a glass to hold water. We flow to the deep. Without you, we have nothing, not even us. That's why we want so much."
As I've said, he's in dire need of a reality check, both in terms of how insulting he's being and in the "you know, everything doesn't revolve around YOU" variety. After all, Sera insists she's just fine the way she is, and Solas can't talk her into feeling otherwise. All of the "elven glory" stuff isn't interesting to her. Solas might insist it's because people like Sera have no concept of what was lost, but I'm sure he'd rather believe that then consider that she might know exactly what was lost and still not care. The little people just trying to live their lives would, I'm sure, rather be left alone.
Considering that he threatens the whole world, I think we've moved past "insulting"...
Still at this point this is just getting silly. The whole "he needs reality check" thing. I know that people can be biased no matter how intelligent thy are, but do you really think that someone established to be a very thoughtful, introspective individual didn't think about all these things you now mention? Even Patrick Weekes in one of recent interviews for Can't Talk Media said that he hopes that even people who don't particularly like Solas recognize that he's smarter than that ("on some level most people think he's smart enough that he shouldn't believe his own BS").
Which of course brings a question of how much really is at stake that even in a world-state where Inquisitor is a good influence on him he decides to continue with his plan. Needless to say, it's likely a bit more complicated than just a wish to bring things to how they were.
Also - *twice* in the game Solas admits (first to Inky, then to Sera after ToM) that as much as he pities her, he also envies her. So yeah, not that simple...