What are the chances the Warden is still alive during DA4?

This is just idle speculation. The Warden finds a cure for The Calling, and settles down to a long, happy life with their beloved Morrigan, three charming children, a dog and two cats in a modest little cottage near the Orlesian border. The Warden takes up a life of quiet farming, and potters around the garden tending the vegetables and shrubbery to the end of his days - and he lives a long, blissful long life, blessed by the strength of their love for one another.

Morrigan abandons magic altogether and is content with her needlecraft and watercolour painting. Embracing the Chant, and finding true peace in the Maker and his Bride Andraste has worked a startling change upon Morrigan. She adopts an air or quiet, optimistic reflection, her old harshness is a thing of the past, and she's far more likely to greet visitors with a welcoming smile and an offer of tea. She lives to a ripe old age, and enjoys ruminating with her mother Flemeth during her frequent visits, always bringing small gifts and sweets.

The couple's first born abandons his silly old god pretensions and becomes a hedge mage, concocting love potions and health poultices for grateful Denerim residents. This makes him rich, and he uses the money to open the city's first hairdressing salon.

This is canon, all know this.

Any so-called alternative lore is pure nonsense.

Well Dwarves are rather short. I suppose that ruling from behind the throne would keep her nicely hidden. All anyone would ever see if they craned their necks would be the top of her head.

My impression was a combination of Blood Magic and actually being in the Trenches. Garahel was never implied to be a bad fighter, but he was implied to be the Face of the Wardens, an absolute golden charmer that needed to be running around talking to Nobles about support for the war. I feel like he only took part in the Big Important Battles, and skipped out on the smaller skirmishes in between.

Which says to me that Exposure and Duration to actual Blighted Creatures plays an effect. To go along with age (although i doubt that one now, as Loghain has been said to look his best in DAI, hardly the worse for wear just because he was older when tainted.)

I mean. I get you? But, otoh, Iron Man is a bad example. He was introduced in 2008 and is still a focus of the films ten years later, as he is still very present in the franchise. It's not like there's a lot of 'tell, no show' with Tony, he shows up to this day in the movies and takes a very active role.

The Warden is like if we had Iron Man in 2008, and then never saw him again, only hearing about him from other characters. 

By the same token, I suppose Bioware has also avoided the Iron Man-fatigue that some parts of the MCU fandom apparently experience with the Warden, so there's that.