I've found that for maps where there is an attack team and a defense team, the defense team is much stronger WITHOUT any engineers.
As of now, the good players have enough experience dealing with sentries that they only pose an hinderance now.
When a sentry is too close to an attach team enterance, one gurella demoman can take it out with about 4 stickies detonating at once. If sentry is farther back, there is a multitude of ways of destroying even lvl 3 sentries.
A barrage of solder rockets will make short work of sentries, especially with crit hits. A couple of snipers can also destroy ill placed sentries that don't have good cover. Combined with good spies who place a sapper on a turret, then cloak away, the attack team can shoot the turret while the engineer is wretching life back into it. (espically when using some ubers)
However, a great engineer on the attack team is very awesome. Teleports, depensers, and a sentry gun to move the offense line up, are very helpful in the push.
Of course, great engineers on defense, are worth their weight in gold, but when I see 4 engineers on gravel pit, I cry inside, and I know we'll lose.
