I was playing "Burning Tide" today, which, for those who don't know it, is a map similar to the campaign scenario "The Devil's Playground", on Redstone III, first of the Covert line missions, in which the winners are the first of the two teams of three players that manage to gather 15.000 minerals, with the additional possibility of eliminating your enemy (the melee techtrees are available), it is currently a featured map on, at least, Europe. Given that, in this map, players are limited to an initial base with only 7 mineral fields and a single Vespene Geyser (8 fields and 2 geysers are available in melee), and, as such, the conditions of playing are different, you'll take of this story an example, or not.I found it fun to play as Zerg, which I usually don't play because of this horrible track called Zerg 7 (you can find retail tracks on YouTube, luckily this map stops the music every once in a while) -- who would have known that music could be a reason not to play a race --, because of all the annoying moves possible with Metabolic Boosted Zerglings. Anyway, with only a single Vespene Geyser available per expansion, you don't see a lot of high tier units. So by the end of the game, my allies had been defeated, and I was next to a ball of over 20 Marines. I had little less than 20 Zerglings, 5 Hydralisks, 3 Roaches, and your so-hated Banelings. Guess what, Banelings were my salvation; the Marines just fell in a mass of green acid.Later, the enemy attacked again, this time with 5 Siege Tanks and a few Medivacs. I had previously used the ramp for a line of sight advantage, I attacked when he was climbing it up. This time, he was smarter and deployed his Siege Tanks in a range that would have hit my army if I had attempted the same move. So I retreated back to my Hive, and waited until he moved his Siege Tanks to attack (I had an Overlord nearby). Again, the Marines fell easily to the Banelings, and the four Hydralisks that survived destroyed the tanks.I played another game later and, again, I had enemies who massed Marines. I must have had over 20 Zerglings, but I had no Banelings. Fortunately, I had a Baneling Nest and I had researched Centrifugal Hooks just in case, so I ordered a few Zerglings to mutate. A few seconds later, my Baneling Nest had been destroyed. In spite of having 2/2 upgrades and the Marines having 0/0, Combat Shields, and Stimpack, my Zerglings fell ridiculously easy to the Marines. I ordered the few that were still alive back, along with a Roach or two, just as the Banelings had finished hatching. And again the Marine ball fell acidified.
You can't send Banelings in a pack without Centrifugal Hooks in an area without creep and hope they reach the enemy, like most people do. I made sure my Zerglings were alive because if they weren't, the Stimpacked Marines would have been completely free to target the Banelings, and I would have been lucky if I had killed 3 or 4. The trick is to get as many advantages as possible, such as line of sight (ramps) and creep.Then again, I was lucky that the Terran didn't move his units, and this was in a game without Marauders. I imagine that in the normal game and against a more skilled player this would go differently, and I would have no idea what to do then, so, like I said, you'll take of this story the lesson you want, but this is just to say that Banelings are not completely useless, like you seem to be claiming they are.