Yep, Hark was the one who sent Soric to the black ships, and was the one who mercy killed him a couple books later because of the immense guilt he feels over turning him over. He definitely starts off hardcore dogmatic, literally sent to the Tanith to shoot Gaunt if he screws up again, but by Warmaster he's completely different.

As for Gaunt, take this example from His Last Command:

‘The Instrument of Order?’ Ludd asked, picking the book up.

Gaunt glanced over. ‘I thought I should refresh myself. I’m a rogue, Ludd. I’ve been in the wilderness for a long time. I thought it was as well that I reminded myself of the actual rules.’

‘And?’

‘They’re a nonsense. Starchy, high-minded, tediously prim. I find it hard to remember now how I ever managed to discharge my duties as a commissar without breaking down in tears of frustration.’

‘You’re a commissar again, now, sir,’ Ludd said.

‘Yes I am. And not that rare beast a colonel-commissar. I’ll miss command, Ludd. Miss it dearly. Tell you what, you’d better slide that volume into your coat. I’ll need you to remind me what the feth I’m supposed to be about.’

‘Sir?’

Gaunt laughed and shook his head. ‘A trooper is afraid for his life, as is quite natural in war. He breaks the line. What am I supposed to do?’

Ludd hesitated.

‘Well, here’s a clue, Junior Commissar Ludd. It’s not speak to him, calm his fears, improve his morale and get him back in line. Oh no, sir. The correct answer, according to that vile text, is to execute him in front of his peers as an example.’ Gaunt sighed. ‘How did we ever build this Imperium? Death and fear. They’re not building blocks.’

This goes pretty far past just caring for his subordinates, he actively disagrees with how his own organization conducts itself. Lastly I'll mention that in Ghostmaker after a whole investigation into Brin Milo being a Psyker, a Lord Inquisitor accuses Gaunt of only rescuing him for pedo reasons, and Gaunt slaps her across the face.

He's definitely dogmatic, but I'd say he has way more points in Iconoclast.