The champion wears heavy armour for protection, but his damaging attacks require such agile swings, swirls, spins and footwork that it is hard to imagine he could do that with any kind of speed wearing the cumbersome legplates that are part of most heavy armour sets. For my champion I chose to combine his heavy chest piece with cloth leggings. Not only did it speed up his moves considerably, it looks great too! 😀
Some players cringe at the thought of combining heavy with light armour, but I think it is quite justifiable and makes for more varied outfit options.
When in combat, he takes off his cloak. The armour looks great from the back as well!
Chest: Hauberk of the Galadhrim, grey dye (crafted, heavy)
Shoulders: Noble’s Shoulder Guards, grey dye (crafted, heavy)
Hands: Noble’s Gloves, grey dye (crafted, heavy)
Legs: Cotton Leggings, grey dye (crafted, light)
Feet: Noble’s Boots, grey dye (crafted, heavy)
Back: Cloak of the West-tower, grey dye (Annúminas barter, light)
Cosmetic Lotro 
I’ve always considered this with my elf, he has to move swiftly, but also needs heavy armour.
I think I mix and match types all the time. I’m more interested in what looks good, but if I were rp’ing, I’d pay more attention to what would work mechanically 🙂