It is interesting and rather ironic to see the double standard at work here. A man can show off his chest and that is perfectly fine but when a woman does it, it is heretical, politically incorrect, objectification, practical concerns, etc.
Talk about selective equality. When it suits you, it is equal. When its not, its fine to have impracticality and objectification. 
First off, both men and women get objectified. The same applies to video game male and female characters. It just so happens that most men who get objectified have the common sense to not take it seriously while women stir up a racket.
Practically speaking, I don't think that outfit should even count as an armor. No good armor exposes the heart and chest of the wearer. So if Varric needs to wear it, he can wear it while he is in Skyhold or just visiting places and not expecting combat.
Maybe if Varric is a mage he can cover himself in magical armor like Rock Armor or Arcane Barrier but he is a dwarf.
As for the claims that this suits his roguish character and his class as a rogue, then why Sera and Cole have no cleavage exposing armor ? Both of them are rogues after all. Sera is carefree and is all about the 'right now' so exposed armor would make sense, no ? Why have we not seen any cleavage exposing armor for the Inquisitor ? Inquisitors can be rogues.
What about characters like Josephine ? She is a diplomatic adviser after all and she should not have to worry about armors. Yet she is all covered up nicely.
I sincerely hope that either one of two things happen.
1) Varric has an alternative armor design that the player can choose to use.
2) We have some cleavage and / or midriff exposing armors and/or outfits options for Inquisitors, for the companions and the advisers.
Because it just seems hypocritical on epic scale not to have them in game.