I find I have a couple roles in objective games that rarely get much credit.
FIRST: I routinely get MVP for flag caps / steals. I'm a ninja on attacking the flag, and have no problem throwing my body on a flag to restart a timer. So what If you go negative in a game you win.
SECOND (this one is big):I'm a really good point man... I'm good at callouts, troop ralleys, timer counts (hills), weapon callouts, and general in game strategizing. The last one is key, because I'm comfortable with organizing a full team offensive - verbally (obviously). This a role most guys assume they are really good at, but most of the time don't realize how quiet they are in game, or they are situation players, that only focus on the battle right in front of them/not the whole battlefield. These things mostly come out in objective games, but in most games I do more talking about what we are doing / need to do then most others on my team and probably like 95% of people we play with (my loud-mouth nature I guess). Metroid is a good example of a middle of the road slayer but a great communicator... How many more kills do you get when you have people like that telling you where everyone on the opposing team is in relation to themselves? Honestly, think about it. The best time to get a full battlefield analysis is when you are dead.. I try and switch through our whole team and rotate their camera to get an idea of where the enemy is / what weapons they hold. If it's 4vs4, callout what your teammates are doing - since your mic never goes out upon death.
THIRDLY: I'm amazing at causing distractions. This is more important in objective games because if you can pull a team away from their defensive positions you can create gaping holes for your team to slip through. This comes in with battlefield awareness, but the idea here is to pull an attacking team's attention completely opposite from your teams attack. This usually ends with your death and 2-3 shield-less opponents, but if timed right - usually begets a score. You'd be amazed at how distracting you can be with a bubble shield.
I agree that slaying is integral to any successful objective, but just having players that focus entirely on slaying is not necessarily preferred. We've lost too many rounds because someone won't abandon their sniper perch or is busy racking up kills (thus respawning the enemy while we infiltrate the base). The flipside to this coin is don't rush if you have the lazer or a full sniper... but when you have killed the whole other team, and you still don't touch / rush the objective that's just selfish behavior and your team deserves to lose.
EDIT: I think I've cont'd this thought through edits like 15 times now

, definitely got me thinking.