While I'm not trying to make excuses for the rocket launcher taking out the AT-TE, in AOTC, if I remember correctly, a Hailfire droid fired some missiles out of it's missile rack that easily took out an AT-TE, who's to say that this isn't a scaled down version of the same warhead technology?
You're right, however that's apples/oranges in terms of comparison... A Hailfire Droid is, essentially, another tank... Scaling down the Hailfire's rockets, why not then just have smaller rockets so you could load a Hailfire up with two or three times as much ammunition, ya know? I mean if they're both equally capable of destroying a large piece of armor from dead center in front, why would you even bother with the larger weapon when you can double-up (or more) the smaller one?
See that's the kind of logic I'm applying... Sure it's just a TV show and all, but it just disappoints me when they go to the trouble of showing a droid sniper with a spotter, and even getting the lingo down to "take the shot", but then they have a behemoth piece of armor get taken out, from the front and a logically heavily armored piece of the vehicle, by a shoulder-mounted launcher.
I could see it from the rear, the top, or the belly... The front just really seemed lame to me I guess.
Also, keeping in mind that Darth Sidious is controlling both sides of the war, it's not like he's going to give either side's forces equipment that will be 100% resistant to enemy fire, if he made it so the Republic could kick the Seperatists asses, the war would have been over in months instead of years and then he'd have to come up with some other plot. He purposely wants the war to drag on and on so that the Jedi are blamed for the war dragging. So what if he puts armor on the AT-TE and then has warheads specifically developed that can penetrate that armor and sells them at an inflated cost to the Separatist Union? To take us even further down the rabbit hole, it could cost him X to make one of those missiles and instead he sells it for 10X to the Separatists and funnels the profit into developing better tech for the day when he finally allows the republic to "win" and he needs to have the forces at his disposal to maintain power/control.
Is Palpatine even involved in the development of equipment though? Again I'd think not, and that he wouldn't try balancing things like that... It's not that the AT-TE can't
be stopped either, it's that it shouldn't be taken out easily where it was. That's just the writers not thinking it through IMO. If one droid with a rocket launcher can do that much damage, why even bother with the armor? There's been personal anti-tank weaponry since there have been tanks on Earth, but they're generally not able to stop one that easily. Bazooka rounds in WW2 often just bounced off German armor. Modern weapons often are designed to hit from above. It just was a moment of wanting an explosion and not wanting to put much thought into it I guess.
There's a pretty established balance in Star Wars as far as firepower goes, and that moment in the toon just seemed lame and off that balance. I don't dislike the idea though, of tank hunter droids like those. Just how easily poorly it turned out is all.
In the OT, a military advisor was actually used quite a bit, especially for the first two films giving his thoughts and input. I liked that aspect of the OT and of SW in general I guess, so I'm always disappointed when anything in goes too simple I think.