My god there's a lot of bitch-assery complaining about a show that has been nothing but awesome so far. I haven't even read the Manga but even I could tell there's more to Eren's "superpower" then him just being the big damn hero. Hell, when you get down to it, he's not even the only one who's "suped" up, Mikasa has borderline super powers, as does the neat-freak recon kid as they're far more capable then normal humans when it comes to killing these things.
Even the Titans have been shown to possess their own Super Powers, both the Colossal and Armored Titans are apparently one of a kind super Titans that only seemed to care about breaching the wall and then vanishing into nothing. Without something more then just the same old "throw people at them and hope for the best" tactics humanity has been using for over 100 years, there would be NO way to progress in the story.
This current crop of recruits isn't anymore special then the previous ones from the past 100 years, so there wouldn't be much of a catalyst for change in the world's status quo. They made a big deal how humans have ONLY won ONE battle in the 100+ years of the Titan's existence, mainly because of Eren's "super power". And he didn't even actually fight anything, he was basically playing the part of a cargo truck while everyone around him acted as defense and decoys. So even with this "super power" they had to come up with a clever way to make good use of it other then simply having him go single-handedly kill every other Titan in the town. There's also the fact that this power is clearly killing Eren slowly and that it's harder for him to return from the Titan state after each transformation, so I can't see it being the one and only tactic they use for fighting other Titans.
Then you're annoyed by things that have actually been explained in the show. There were pitfalls around the gate, they didn't help much. Also, what good would hot oil do against things that can regenerate almost instantly? The Titans have all of one known weak-point and hot oil or heavy rocks or any other conventional siege tactics are capable of hitting that weak point effectively. The only reasons the cannons work is because they're firing high explosive shells that can actually destroy the weak spot with enough sustained fire. If anything, being able to fire directly down with the cannons gives them an even bigger advantage to most other weaponry as it gives them a better angle at the back of the Titan's necks.
Also, the inner wall was never intended to be involved in such extreme siege combat, they went 100 years with just the outer wall working just fine as their main defense. It wasn't until the unexpected breach of the wall by two super-powered Titans that they realized they needed to add defenses to the second wall. And with the 5 years they had to work with, cannons on rails and pitfalls near the gate were the best they could come up with.
I marathoned all 13 current eps in one sitting after finding out about this show, and I really want to see more of it. I'm tempted to grab the comics, but as others said, the presentation of the Anime makes it a far more visceral experience. I'm sure I'll grab the comics in time...but I'm not sure if I should wait until after the show ends (in case it DOES have a different Anime ending) or just go spoil all the fun to see what happens while getting the details the anime was forced to skip over.