This post is actually about motivating and rewarding desired behavior. I think most people would agree that it's desirable for people to put out their strongest defenses and to feel that 3-trophy, more challenging fights are generally worth the effort, over 1 or 2-trophy easier fights, or at least that the rewards match the risk/effort/time.
However, when you look at the reward system, the motivations work the other way. Certain rewards scale up with "challenge" such as glory and money (but not fast enough), and two very important rewards do not scale at all: traitstones and Guild Seals (they are simpliy awarded per battle, not per Troop defeated, and do not scale up from 1-trophy to 3-trophy fights).
I've found when I tune a team to rapidly take out a 1-troop defense as quickly as possible (ideally a 1-Elspeth Defense), my overall rewards per hour vastly outperforms anything else I can do. I can do about 65 of those battles per hour, as opposed to about 20 battles per hour using my fastest "3-trophy" team, which takes me on average about 3 minutes per battle to complete.
With 65 battles per hour using the "1-troop" technique, it means I get about:
1. 4-5 times the gold per hour
2. 3 times as many traitstones per hour
3. 3-4 times as much glory per hour
4. 3-4 times as many trophies per hour
etc. etc. There's actually no reward that doesn't come in at a very significantly faster rate, except perhaps souls... but as I now have something like 600k+ souls I no longer track that at all.
So, the point of all this is: the reward system might be reconsidered in a fashion that rewards a win against a 3-trophy, 4-troop Defense in a way that makes it more attractive than simply playing a rapid set of 1-troop, easy wins.
Now, I know many people will say "but I only play 3-trophy defense teams for the challenge. Anything else and you're not doing it right." And for those folks, the challenge of those fights is worth earning 1/3 to 1/4 the reward per hour played. But my own play is tuned towards what winds up rewarding me the most over time.
My main goal at this point is to trait out my troops. And for that, what I need the most are battles, not "challenge" and I can get 65 battles/traitstones per hour with this technique.
if they rewarded 1 traitstone per Defense Troop killed, for instance, then of course it would all turn on it's head, and suddenly you'd be looking for 4-troop Defense teams as you could make more per hour doing that. Or, perhaps the quality of traitstone improves - that is, the chance of getting an arcane and such goes up with the 1, 2, or 3 trophy fights.
Anyway, regardless of the exact tweaks, I'm just pointing out that the current reward system seems to motivate the fastest possible cycling of battles, vs. winning over the most challenging Defense teams. I'm not sure that's really what they intended, but it seems that's how it plays out right now.