So, I was thinking, there's general guidelines in E6, much like there's general guidelines in 4e.
Defender: Capable of attaining 28 AC or more (9 plate armor, 2 heavy shield, 1 dex, 3 natural armor amulet, 3 deflection without too much twinking). Capable of having more than 100 hp either through innate healing themselves, or abilities to recover hp without the aid of others.
Striker: Capable of dealing 100 dmg in a round consistently
Skilled: Capable of dealing with traps, skill checks, with more than +13 to the relevant check. (9 ranks +2 ability modifier +2 masterwork tools) in multiple skills on a regular basis. For example, a mage could deal with traps by summons, but would run out of spells eventually and thus not fit into this category all the time.
Controller Capable of casting 3rd level spells for problem solving, battlefield control. This includes things like artificer which uses wands of 3rd lvl spells or similar.
Leader: Capable of party enabling, healing, buffing, etc. Note this does not apply to PCs who only grant it to themselves mainly, and should not be considered when balancing. Or if the PC mainly enables the party with their actions, they could be considered, losing a tier due to actions placed into non-combat related things.
Alrighty, so I'll be using Yan as an example, she has 117 hp, and can share pain with her psicrystal or empathic transfer.
Defender: Tier 3: While she has 50% miss chance for incorporeal, she has only 18 ac, much less than the typical fighter in plate armor in E6. So she comes out as Tier 3 in this category, really good at one thing (hp and healing) but not as good as others (lowish AC and hp).
Striker: Tier 4: She can melee, but unless she cheeses out the collossal arrows, the 100 dmg/rd is very hard to attain for her, and makes her lose out on other aspects.
Skilled: Tier 3: She can't use many skills but the standard wizard knowledge, and traps aren't beatable to her on a regular basis. That said, she does have a high charisma for many charisma skills.
Controller Tier 3: She can grapple, probably the best in E6, for 1 vs 1. She sucks at multiple opponents though.
Leader: Tier 2: Short of an artificer, she can do the best stuff, and more tricks of them via leaching psyche, and echo effect. I only placed her in tier 2 as she doesn't have as many options unless others have brought them.