Have been testing Raider for two days now.

First attack says it will hit twice if the targets HP % is higher than this heroes. It does not activate at all, regardless of HP %. Tested in both arena and campaign mode. Have tested this when the enemy is full HP and raiders is below 50% to rule out ambiguity and have also tested the opposite way in case it was a tooltip mistake. Never attacked twice.

3rd skill says chance to stun for 2 turns and chance to reduce def for 2 turns. Whenever either of these proc, they are only for 1 turn. Tested this multiple times on manual against heroes who'd just taken a turn to ensure the target wouldn't take a turn immediately afterwards. It's only ever 1 turn.

Finally with the 3rd skill, the tooltip may be unclear, but as far as I can tell you never get both stun and decrease defence proc on the same turn. It seems to be either one or the other. Understanding the % chance of 2 x .6 and having witnessed one rebuff successful at least 50 times, I would expect to have seen it proc both at the same time. If the intention was to only make it one or the other, the tooltip needs to be re-worded.