It’s too bad we didn’t get Sandal as our runecrafter in Inquisition. That would have freed up Dagna to be our dwarven companion instead of Varric.

Bear with me.

• Solas was looking for an Orzammar dwarf to have particular conversations with and Dagna fits that bill. Conversely, she would have any number of questions for him about the Fade, at least some of which he would be able to answer.
• Banter with Sera would let their relationship develop in front of us instead of happening offscreen.
• Sera wouldn’t let the Iron Bull throw her into combat and Varric’s too stocky…but Dagna could do it. Not only that, but she’d have invented some things to make it easier for Bull to do so. Either that or she would have refined Scout Harding’s “mounted dwarven archers” idea. Probably both.
• Dagna’s from the smith caste, so she could discuss armor with the plate-wearers. Imagine the conversation with Cole and Cassandra about her armor with Dagna chipping in. Cassandra might eventually let Dagna add some of her…tweaks to said armor. Might.
• Dorian and Dagna would come up with as many fantastic new ideas for combining forces as Sera and Dagna.
• Vivienne would be able to talk to Dagna about her experiences with the Circle, since Dagna is certainly in favor of its educational aspect.
• Dagna would no doubt be VERY curious about Cole. A real live spirit from the Fade that she can talk to and ask questions!
• Blackwall would be relieved that Dagna’s previous experience with darkspawn was actually less than his own, so he’d open up to her pretty quickly. Crafting buddies! Imagine the things they could create together. Plus bonus banter regarding the Sera/Dagna pairing.
• Dagna’s already involved with the main questlines for both the mages and the templars. Imagine how much more they would be fleshed out with Dagna actually present. Dagna studied with the Tranquil in the Circle; surely she would have had something to say about Maddox. Plus all that red lyrium and time magic. Calpernia had used dwarven memory crystals; wouldn’t Dagna have benefited greatly from being present for more of that quest?
• Dagna would lose her shit at Adamant. Actually being in the Fade is a literal dream for her. Now picture her and Solas squeeing while unfortunate companion #3 wails in distress.
• The Descent would also benefit greatly from Dagna nerding out over everything. We might even get a few answers on what happened with Valta.
• She would also lose her shit during the entire duration of Trespasser. Dagna already constructs things that are half-in and half-out of the Fade. The Crossroads are right up her alley. She’d also undoubtedly be the only other companion to Cole to approve of saving Solas, providing some extra perspective amongst the companions.

Dagna would have been a ranged rogue, using runes for traps among other things. She’s not a heavy combat person, but I bet she wouldn’t have minded a little personal field testing for her inventions.

As for Varric, he could have hung around Haven/Skyhold without having to muddy his boots tramping around Thedas. After all, he still needed to bring in Hawke. But he didn’t have to be a companion.