Enough Magic Poured Into The Mark...

I know you're looking for a serious answer, but everything went downhill when I thought about Templars trying to suppress the Breach by reinforcing reality and then likening it to sponging up Fade energy.
*Inquisitor grabs a Templar and tries to rub the poor guy on the Breach*
"It's not working! Hand me another!"
"We're running out, Inquisitor! And I don't think this is how you close a breach!"
"Nonsense! Come on, our stalwart allies! Prove your powers of absorbancy and soak! Soak that Fade energy like the grease cutting detergent sponge you are!"

Templars suppress magic. If you play through the Champions of the Just quest, the is a cut scene where the Templars plunge their swords into the ground (very much like they do at the Temple of Sacret Ashes to weaken the Breach) and weaken the barrier protecting the Envy Demon, eventually dispelling it.

I guess I was trying to find an analogy and failing. When they reinforce reality, are they dispersing energy? Forcing energy from the material world into the places where the Fade is leaking through? Is it simply scattering it, dissolving it like dish soap on greasy dishes?

The funny thing about the cutscene is that the sound the Mage staves make when they hit the ground is the exact same sound the Templar swords make when they strike the ground. You would have thought Bioware would at least change that.

Just one thing - How does one draw willpower from someone ? If the Herald is a mage, we can justify that with magic but how does a mundane (that's the term World of Thedas uses to describe non-magical people) Herald draw willpower from someone ?

Good question, lol. I guess still magic? The Inquisitor is less mundane after their little fade trip and receiving the mark, which they just seem to get the hang of quickly. Or if the Inquisitor is receptive enough, the mages/Templars are projecting their willpower onto him/her. 

The Orb - and by extension, presumably the Mark, since it was created by using the Orb - require a vast amount of power to function: Solas says his plan was to get somebody to unlock the Orb for him, since he was too weak to do it himself. So at least my theory goes that the reason the Inquisitor almost dies when s/he tries to close the Breach for the first time is because there is nowhere near enough magical energy anywhere in the vicinity, and that's why the Herald almost kicks it.

So IMO, in that light, having mages give the Herald more juice to wrestle that thing into shape makes perfect sense to me, and at least sounds like an improvement on his/her safety. Then again Cullen also has a point, but although I have played IYHSB through with Templars, the logic of "suppressing the Breach" kinda escapes me.

Then again there's also the fact that absolutely nothing guarantees that whatever they do actually works and closes the Breach, not to mention there's always the chance the Breach starts spitting out majorly pissed off high-level demons the moment the Herald walks up to it which end up ripping him/her into shreds... and with all the other shit the Herald has been through (time travel / stuck to the Fade etc.) I'd think that at some point the Herald would accept that his/her life expectancy has dropped pretty dramatically since s/he got the Mark regardless to what happens to the Breach, so s/he might as well close it.