I think the shard rewards for this event are getting too diluted due to having so many potential units you can get. If people want Range Trooper from this event, the odds wouldn't be great at present. I've considered adjusting some of the Assault Battle rewards to behave like Rebel Roundup, where each tier is a thematic block of units and then the bonus is all of them. Would you guys be open to that? (Note that any such change would require signoff from the boss, and wouldn't happen for awhile since the next several updates are already being worked on and this would go on the farthest-out update.)