Playtesting the Ridgeback

During hiatus I'm revisiting the WWtH monsters and trying them out in actual 4e combat encounters. With the party at first level we tested out the beelion, the doppelganger freak and the laughing lambchop lizard, then tweaked the latter two and ran them again. After leveling the party up to level 2 and giving them appropriate gear, we've started in on the level 2 monsters. The party is still:
A goliath warden
A gnome bard
A longtooth shifter ranger
A deva invoker

Last week we got through one encounter showcasing the sabre-tooth lycotaur. This week we tried out the ridgeback loper. The map was still Teleport Temple from the War Drums Starter Set. The party started in the top center of the image to the left, hanging out outside the room after their encounter with the lycotaurs. Since I liked the frightened screaming wizard so much last week, he ran by again. "A wizard runs around the corner yelling 'Goblins on giant lizards are attacking! Aaah!' Roll for initiative."

The encounter was two ridgeback lopers and four goblin warriors, with two goblins mounted on each loper in side baskets like in the picture on the monster entry. Oops, looks like in trying to alter the encounter to put in evil enemies I missed the "rider nth level or higher" rule that mounts always have. Oh well, it's a weird rule anyway. The first loper was spotted in the opening just below the square wall/pillar/whatever. The party (except the invoker) won initiative and charged it. Then the second loper came around the corner at the top left of the map and its goblins started throwing things at the invoker.

Surrounded, the bard and invoker ducked for cover and plugged away with their ranged attacks. The ranger and warden pretty quickly dispatched their loper and scattered the two goblins. The goblins moved next to the nearby teleporters and the ranger and warden obliged me by missing each of them, allowing them to use goblin tactics to shift into the teleporter and blink away to the upper right corner where they could join in the harassment of the other two PCs.

Meanwhile, the loper-and-two-riders arrangement was turning out to be quite vulnerable to the invoker's area attacks, but the invoker was pretty vulnerable to their highly mobile return fire. The loper fell first, however, and the deadly bard followed up by using an action point to viciously mock both riders to death in one round. After that the party easily chased down and mopped up the last two goblins.

The lopers were probably too constrained by the tight hallways on the Teleport Temple map. They were pretty effective anyway, granting their two riders hefty attack and damage bonuses almost every round (especially the second one, which had more room to maneuver). If the battle had taken place on a wide open outdoor map, I'm sure the PCs would have taken a lot more damage from bonus-laden missile fire.

The encounter composition raised one interesting question, though. The goblin warriors get +1d6 damage if they move more than 4 squares due to great position, but the loper also grants +1d6 damage with hopping gait if it moves more than 4 squares. I presume the warriors get the bonus even though they're not using their own move since it's just based on distance from starting square, but then do the two damage bonuses stack? I was ruling that they didn't since it seemed like an overwhelming amount of damage if they did, but I'm not sure that was right.