As has been said, kills are essential to objective gametypes, but I don't think they need to be specifically recognized or rewarded if the objectives are sufficiently recognized and rewarded. It's not like people are going to stop going for kills if you don't give them a cR bonus, or a medal. Everyone is going to slay as much as they need to to accomplish the objective if it is sufficiently recognized and rewarded. Instead of "[MULTI KILL]!", or "[SPREE]!" being shouted at the player, give them useful tactical feedback, such as the number of active players on each team (perhaps with a visual indicator just for objective games) that they can make informed gameplay decisions.
If I were more skilled in graphic design, I'd make a mock-up of an objective-specific graphical interface that gives real-time pertinent information, so that at-a-glance I could know the current status of the game:
OUR FLAG (HOME, AWAY, DROPPED w/distance to cap point) -- 3 boxes with 3 unique icons
THEIR FLAG (HOME, AWAY w/distance to cap point, DROPPED w/distance to cap point)
ACTIVE PLAYERS (4 Blue Boxes, 4 Red Boxes, colored squares that are filled in when players are alive, and have a respawn countdown when they are dead).
Furthermore, all team members should be equally rewarded for each objective game milestone, rewarded for winning the match, and should be given bonuses for speed (the faster the victory, the bigger the bonus).
And of course, kills and deaths from objective games should not be counted towards a player's overall kill/death ratio (you'd think they would have made this decision when they made Grifball a permanent playlist).
