Whats happening is your team is taking to long to destroy the hive, so they start spawning in rhinos that will pretty much destroy you stopping your progression.
Make sure the chopper stays "Engaged" with the hive and not "Evading". To keep the chopper engaged you need to keep the scorpions from shooting at it (Kill all scorpions). It will also help if your team lays some rounds into the big bulb on the hive itself(You get hitmarkers), along with any kind of explosives to help take the health down faster. (Turrents, semtexs, SOFLAMs, Deathmachines, etc.) Hope this helped.
Ps The scorpions can be crafty in their locations. So make sure you keep the roof clear as they like to jump on top just out of sight if you are down on the street in front of the hive, and they also like to sneak in behind the hive in between the two buildings. Automated Sentry's can be your friend here, I always aim a sentry right at the hive so if any scorpions jump around back there they either get killed or they run off.
This means you are taking to long, as previously noted by BamBoozeLLed. I suggest you invest in grenade launchers, Death Machines, etc. to help the chopper take down the hive, by this point you should have maxed out your sentrys and be able to place 2 sentrys, if you have 4 members with sentrys, you can put down a total of 8 sentrys, this way they can cover you as you jam ammunition into the hives.
Hope this was helpful. take care!
Team size does matter, the more players, the more aliens attack you. Basicly, the key is to take down the hive asap. let the sentrys worry about the aliens and put all your ammo into the hive (bombs, turrets, death machine, grenade launcher, etc). If your are a team of 4 and take too long taking down the hive, you would get more rhinos pile up against you.
if its two of you, manage the 4 sentrys asap, and max a death machine each, you will be able to get through in no time. you can each put 200 rounds of the death machine into the hive and be alert when scorpions pile up, scare them off and continue putting down that hive, when i go solo i put 3 death machines into the boss hives and the two sentrys behind me taking care of the aliens that approach.
Tip: you can take out a rhino with a death machine that is maxed out, it usually takes 80-90/200 ammo to put one rhino down, so yes, with one death machine you can put down 2 rhinos. just remember to have your armor secure. if you have your sentrys working with you, you can save ammo for the swarming aliens or more for the hive.
Advice, try to have a flare on you, it comes in handy when you run into trouble, they are really really helpful at the very end when you need to evacuate.
never run low on ammo and armor
Good luck Gam3H3ad !
You have approximately 7 to 8 minutes to destroy the hive before the Rhino's appear. A good tactic is to have 2 Sentry Guns in the middle section of the wall in front of the hive that has the electric traps on them. Face one towards the parked car and one towards the hive. Make sure you turn on the electric traps there and keep them on. This way the guns cant be destroyed by any of the aliens. Once they run out out a new one up. If you have more people with sentries thats even better. Just put them just in front of the hive facing out but a little more to the left and right. As long as you keep killing the Scorpions and the Chopper stays engaged as Bamboozlled mentioned, the hive will be destroyed before the Rhino's appear. This way you can maximise your kills and score. But as previously mentioned by hitting it with your weapons and other items it can be destroyed much quicker. Even an upgraded mini gun will destroy it with a couple of them in about a minute or two.
You have 8 minutes to kill the hive before Rhinos appear; it's not hard if you place several Sentries / IMS and have one guy shooting at the hive with everything he got; I've haven't had this issue since I started to focus on the hive more than the aliens by the use of Sentries, traps and IMS.
If you have killstreaks dealing with the mob of aliens, a couple players shooting at the hive and a couple shooting at the Scorpions you just cannot go wrong.
an easy way to keep the scorpions off the helicopters, is to take on the aliens on the roof. I learned this from another player last night, and thought it was pretty strategic, and so tried it and worked for me.
place a +3 sentry by the basket weapon and have explosive ammo, the sentry will keep aliens off you, and you keep the sentry safe, its pretty secure this way. but the primary reason i found this strategic, is that you can really distract the scorpions from hittin the helicopter, plus they do come from the back, mostly. if you have the two pistols and are supplying ammo, you can have a real blast killin the aliens. by doing this it took like 5 minutes to get through the barrier.
However, plowing a few death machines into the boss hive is still way more effective, considering the DM is maxed out.
Good Luck !
it's because you take to long to destroy the hive make sure that the chopper is always engaged, to do that I normally prioritize killing the scorpions first the manly show up on the roofs and on top of the trucks or right next to the barrier hive. I also suggest putting down many sentry guns preferably upgraded, and if you are not a high enough level go to the roofs where the scorpions are and there is a turret facing the hive that you can shoot at it with, also it would help to have more than two players I think but then more aliens come so it depends on your equipment.