**First I want to say that I have not been playing since the Beta, I bought the game on Launch Day 2 and have played it almost exclusively ever since. That being said:
The ninja plant I propose is simple and can be effective. It relies less on spending all of your time just sitting at C and focuses more on getting to C after the first 2 objectives have been taken. It also relies heavily on you playing with a clan/friends/etc. who will actually listen to you and what you say (if you play on a squad of trusted players you probably win alot already).
Now when you are on Alpha or Bravo squad and are attacking A, as soon as you start to take it you will hear something along the way of this from Charlie and Delta "Come on guys PUSH UP, they're already taking A!" And (its happening more often that) they will sometimes muster the courage to charge and take B. When this happens the enemy team is pooping themselves...
On defense I often witness EVERYBODY running EXACTLY the same way when either their objective is being taken, or ESPECIALLY when theirs is being taken after the other has already been lost. Anyone who does deviate from the herd is usually all by themselves.
So what the F does all this boil down to? Why have you been reading this the whole time? Because now that you understand some of the basic psychology of the attacking and defending team you can take advantage of it. If your squad is Alpha and A has already been taken, as soon as B starts to become acquired (make sure on your map that it is the WHOLE TEAM and not some lone wolf who was lucky/good enough to get there alone.), your whole squad must either pop POISON on the key routes the defenders can get to A at, place MINES covering the stairs and doorway to A, or pop SMOKE on the route that your squad will take to rush C.
All of this is done to make up for your abscense at A so that you are not complete **bleep**s to Bravo squad. Once your traps have been laid, you must all haul your butts over to C (yes, while B is still blinking), so that as soon as C does show up you have an easy plant. After you have planted your squad is responsible for dying covering the entrances to C until the rest of your team can join you. It takes around 45 seconds for the objective to blow, most defenders are still close to A or B (becuase they were JUST taken over). Most people will think that it is a ninja plant and that they have some time to get back up to C becuase everybody who just spawned is rushing it. Now a somewhat compotent Bravo, Charlie, and Delta WILL SHOOT THE STUPID ENEMY IN THE BACK FOR JUST TRYING TO RUN OFF TO C, so that will make your squads job slightly harder, but the rest of your teams job's alot easier.
"Um...so?" So your squad has to kill only a small portion of 32 people, maybe around 10 initially after you have planted. There will be huge rushes through the door in about 15-17 seconds, plus the time it takes the enemy to run to C. By this time the clock is down to around 20 seconds or so. The rest of your team is coming to assist any second, if they have not made it there already. From this point it is as if your team is defending C like they were actually defending from the start (lol).
Commandos don't lose, we just blow stuff up!
I've tried to get people to do this. It would help if Platoon Leaders would talk to each other.
A already is taken and being guarded.
B is just about to be taken and Platoon Leader talks to A Platoon Leader to let him know that B will be taken over and to start moving to C.
Communication and teamwork (outside of squads) is still severely lacking in this game.
The problem would lie in prevalence; if this became flavor of the month for a few games, defenders would adapt and counter when C is about to open. It happened in beta and people whined for a while and then they just adapted.
To answer your question:
It's a viable strategy and not really unfair as it takes man power way from the fight to do it in the first place.
Early planting used to be easy in beta. Now, it's kind of expected. But that's good.
However, it works now and then.
Last night we attacked SVER. I ran from B to C as soon as I saw A going down because there was no way my objective was going to fall soon. I early planted and killed 9 SVER guys coming to defend it. This was enough time for my boys to get there and help with the wave of SVER players flooding in. Seconds later, it blew sky high.
So yeah, if you can hold off just over a squad on your own, it can work. On defense, I always tell people to run back to C the instant the second objective starts to fall and haven't been on the receiving end of a quick plant since release.
I think the main way to be successful is to make sure that you stall at C until the plant goes off... Stalling tactics are different than killing tactics. I suggest doing this with 2 or 3 ppl at least.. 1 will usually get overrun just too quickly...
But 2 ppl can put 4 anti personal mines at C. These stay active until you spawn again (and I've heard rumors that these stay if you come back in a loadout that includes anti personal mines, but I haven't tested this yet.) So 4 anti personal mines strategically placed to kill the first 4 ppl planting.
Now most ppl I've seen typically let these personal mines take the first few deaths and they try to mop up the rest... this is backwards, and is where the stalling tactics come into play. It doesn't matter if you live or die, because you still have 4 mines for the first 4 ppl to try to plant... what you should do is cover where the newly spawned wave is arriving from and get them to look away from C. Attack from a bit away, but close enough they will chase you. Throw nades between them and the objective to clear the first few and get their attention, then maybe an lmg or smg (or knife if you're good at that) to keep their attention...
Whatever you do, you MUST have the plant last an entire minute!!! If you don't do this 80% of the time, you need to work on a new strategy that will get at least 80% success rate.
btw this is especially important on Valor map, because their C usually takes up the bulk of the sabo games... Raven C isn't so bad, as 1 strong rush can hold it until it bombs. SVER is a mix between these 2.. You can get into SVER okay, but holding it isn't always so easy... so ninja planting here is helpful but especially on Valor this should be the strategy.
Specific strategy to the Valor ninja plant - first take 2 ppl. 1 needs to be a good sniper or lmg gunner. Get into the top sniper roost with the ladder that has a bead on anyone running from the A side spawn up the stairs across the scaffolding. Here it's pretty easy with a 1st or 3rd tier sniper, or either heavy gun to mow down the entire spawn. The other guy needs to watch the stairs to the left of C (facing the console) MOST of the attackers will come through here. Plant 2 anti personal mines to cover each stair case, but be ready to machine gun and nade the left one. Gas nades are great, but be sure to throw them early. They take a bit to provide cover and damage, so don't wait to toss these out.
A 3rd person for Valor ninja planting is VERY helpful. 6 anti personal mines, 6 nades, and 3 lmgs can go a LONG way toward holding this for a minute.