While yes, the carrot in Semi is placed in a rather awkward posistion, that doesn't change the fact that it's your only option for healing. Attacking a camper there can still be difficult because if you hit them, they'll just take it for themselves and make a quick escape and/or finish you off. A skilled camper there can pretty much defend all of the routes simultaneously anyway. There are few "effective tricks" yes, such as long range EB shots to shoot the carrot down and obtain from underneath, although those sort of tactics come with a high risk and unless your opponent gives you a large opening and/or you're extremely quick, you will probably get killed in the process.

What I'm trying to say is that levels with only one carrot tend to rely on hit-run-camp tactics which focuses all of the action around a single point and therefore less of the level is used during the gameplay. Levels with more than one carrot involve more hunting and quick reflexes, which, in my opinion, leads to more active duels where prediction is vital, more usage of the level and thus more fun.

Of course, these are only my personal views, some people prefer levels with only one carrot as it means it's easier to kill someone if you have skilled dodging and time your hit exactly right. However, levels with multiple carrots can still be easy to control too, just as Troglobite suggested, just with the difference that you don't have to rely off just one carrot to heal. All of this applies to duels only though, in team games having just one carrot doesn't seem to be an issue due to the fact there are more players to be hit by and thus being harder to successfully camp.

Basically, the carrot setup decides the gameplay in duels.