As the title suggests, the limit for engineer is currently set to 4, my suggestion is to take it down a notch to 3. Reasons for this are as follows: A few maps heavily help out the red team, mainly the smaller ones like military area and skyhigh resort where even bosses with stun rages find it very hard to take out the sentries or the engineers, forget the bosses without them. Knockbacks on the boss are an issue especially when the servers are highly populated and the amount of engineers are a good cause for it, hence causing bosses to lose health very quickly. Engineer is a relatively powerful class capable of doing a lot of damage and couple that with heavies and other classes that normally tend to camp around them, we see a huge downside for a boss. We used to have the limit at 2 a while back and it was fine, 4 is just a bit too much so 3 is a good thing to go for and we can see how it goes.