I think the champ mechanic is not fulfilling its purpose right now of providing increased challenge. Champ mobs are basically just trash mobs that take two extra hits and drop rems. They're not a challenge, they're a bonus.
I think if champs not only boosted themselves but everything around them, they'd be closer to actually moving the needle for players, forcing them to react and modify their behavior. And that would become even more acute in higher difficulties where champs are more prevalent, as it should be, since their auras would stack - discouraging zerging or herding.
They should be strong enough that one alone makes a difference, and two or three could turn the tables - thinking like +20% damage, +50 prr or mrr, +15% speed, +50% max hp, stacking bleed on hit, -100% fort, 25% deflect arrows, 20% kd-on-cast-guard etc. Some general, some more or less deleterious depending on your playstyle.