I'm having trouble using these guys effectively. They never seem to do enough damage on the charge and tire out very quickly. Any tips?

sounds like you're playing them at a very low level, what level game are you playing at?

One of their most powerful abilities of these winged ones is their high intimidation you should never attack a new unit, first soften them up with volly fire , or catapult a cow head or two on them or have another unit attack at one angle so their attack becomes a flank.
once their morale has been lowered then fly in and one attack usually will cause the remaining unit to scatter.

Use magic items that beef up their fatigue as they tire very easily in-flight, or when they're flying,opposing units cannot fight back, although they do take missile fire. when I use items I usually only beef up one stat every item that they can put on assets to that one stat, so there is a sometimes up to 300% increase in the stat, most of the time I use stats that are high to begin with, but because they fatigue so fast I usually beef up their endurance. But I also have a set of items that beef up their intimidation making them exceptionally scary.

I use them in endgame strategies I never play on a 4 x 5 battle map I always use a 6 x 7 battle map, and keep them on the back row out of range until I need them. If you play on a smaller map put them in reserve so they're fractured when everybody else is tired and stressed. You should be able to take out three units before they are are exhausted and too weak to do anything else of significance.

see them as a quick strike force that brings a lot of hurt, and scares the hell out of them after. but quickly tires Using him for anything else is ineffective.

I'm only using them at level 5. My understanding is that the fatigue rate doesn't change with their level, though.

I was planning on trying to use fatigue-reducing items on them next time. The basic tension I'm struggling with is that they're pretty vulnerable to shooting when walking on the ground and tire out too quickly when flying.

I'm only using them at level 5. My understanding is that the fatigue rate doesn't change with their level, though.

I was planning on trying to use fatigue-reducing items on them next time. The basic tension I'm struggling with is that they're pretty vulnerable to shooting when walking on the ground and tire out too quickly when flying.

I play a level 40 almost everything unit in Exillis at lv 5 is pretty wimpy, I haven't played that low in so long but I believe units of Spearman and swordsman did the best at real low levels