?? Figuring out an EL for the encounter might be complicated, but that's just a rough-n-ready (and in many cases, flawed) method for estimating the challenge when designing the encounter. For giving experience, just look up the CR of each creature on the chart in the DMG, as stated on DMG pp. 165-66 (where you can find the chart as well). For an average party level of 8 (round down, as usual), the 6th level fighters are worth 1,200 experience points each, the 5th level archers (assuming they are PC classes and not warriors) are worth 800 experience points each, and the 1st level shield-men are worth nothing (of themselves-see note at the end for a caveat). So, the grand total is 20,000 experience points for the encounter, or 4,000 for each PC. (This is comparable to what they'd get for a CR14 creature, which is a good estimate of the Encounter Level. I'm not surprised they had a tough fight ... EL +6 falls into the 'overpowering' category in the chart on page 102; the party was probably both tactically clever and lucky to fight through this wrecking crew.)
If the situation was such that the encounter was significantly more or less difficult than a straight-up fight, then the experience point award should be adjusted per the chart on page 167. The shield-men could factor into this in spite of being worth no experience in and of themselves. I would venture to suggest that the 20,000 x.p. is quite sufficient in this case ... In fact, although of course I can't say without a full description, I imagine that unless the PC's were quite ridiculously lucky, they must have had some kind of tactical advantage going into this combat for them to come out-this could reduce the experience point award to 10,000 or 16,667. I'd consider it, in any case-if this was one battle, they're looking at half of the experience they need to get to 9th or 10th respectively. That would take 13+ encounters of their normal challenge level.
