@Nyte, up to you really regarding defences. I generally think the game is better if you max things before moving on, or you end up getting constantly annihilated in MP and war, but walls are definitely a bit of a slog!
Anyway, here are my sacred scrolls for pekkabobat. Needs max troops; until your pekka get there you can get away with giants, but they're not as good. I use this attack a lot with Sparta. Key is dropping the bats at the right time.
Army composition: 5 healers, 4 pekka, 8 bowlers, 3 baby dragons, 2 wizards, minion. Spells: 3 x freeze, 5 x bats, 1 x poison, 1 x rage. CC should be a wrecker with rage, and either 4 x valks, or yeti plus 2 x valks.
These are the steps:
1. Drop queen plus healers on one corner
2. Drop 2 x baby dragons on parallel corner
3. Drop 3rd baby dragon near queen to make sure she heads in the direction of the 2 baby dragons you've dropped
4. Once queen starts heading in from a corner, and the 2 x babies have taken out the other corner, drop your king in the middle
5. Then drop your wrecker, pekka and warden
6. Once the wrecker breaks through the first wall, drop your bowlers. Don't drop them too soon or they can wander off.
7. Rage everything fairly early so you get the "splash" damage from the bowlers. Use your warden ability to protect the wrecker - it has to make it to the core.
8. Drop poison as appropriate. If there's an enemy cc, on that, otherwise use it to either slow down the enemy queen, or deal with annoying skeletons. Try and save your freeze
9. Use the second rage when the troops are in the core.
10. Once the TH goes down, and the eagle goes down, you're ready to unleash your bats. Remember that they go from defence to defence, whichever one is closest. Key is to drop all 5 spells at once, as far away from wizard towers and multi-infernos as possible. They take a while to emerge, so it can be good to drop them near defences that are targetting other troops. Eventually you will have a bat "bomb" - a clump of bats that take most defences out in one sweep. At this point, completely focus on your bats; they are the key. You need to anticipate where they are going to fly next, and be poised with your freeze. They move fast, so you have to freeze defences proactively. Wizard towers will take literally all of them out in one shot, so if they get anywhere near, freeze them. It's worth playing it safe and freezing them well in advance, and using a second one if necessary. multi-infernos are also high priority as they will take out almost 10 per second. Third priority is tesla farms - if there are 4 teslas close together, they will take bats out really quickly. When you're planning your attack, try and attack in a way that you take out the eagle early, and as many wizard towers as possible. You need to get a feel for when to release the bats - too soon, and they will not get very far plus you'll be thinking of the rest of your troops; too late, and there will be no other troops left so they become the focus.
As a general rule, i will always wait until the TH and eagle are down, and I've done 50% plus. Unless the base is fully maxed and very well designed, you will 3 star any TH11. With perfect timing and pathing of the bats, the cool thing is they will survive until all the defences are down, and make for very fast clean up troops.
11. Drop your minion behind the bats. They can start clean up as the bats will take out all defences.
12. Keep an eye on bats progress, and use hero abilities as appropriate. If you've still got them, use king and queen abilities to try and take out the bats; nemesis defences more quickly (wizard tower/multi-inferno)
Direction of attack
Look to try and choose a route in that gives access to the eagle fairly quickly, and also takes as many wizard towers/multi-infernos as possible. If the eagle is really exposed, go for it. If it's central, it's okay to attack from the opposite side as you can still get it with splash damage. Prioritise wizard towers/multi-infernos.
How it can go wrong
Avoid these things:
1. Dropping bats before eagle is taken out. It will target your bats because that's the most HP in one place. You will lose them all, and your attack will fail.
2. Failing to protect the wrecker. Always drop your king first, and use your warden ability to make sure the wrecker gets to the core. If it's getting close, and is targeted by a single inferno, it's okay to use one freeze
3. However...don't use more than one freeze. Otherwise your bats can quickly die.
4. Don't freeze too late. Bats move super late. One of the most common ways I fail is to lose every single bat to a wizard tower that i freeze....just after he's wiped them all out. Remember that 8 of your spells are committed to the bat part of the attack, so you're heavily invested! Protect those little fellas
5. Queen separating from main attack. This is where your 3rd baby dragon is key. You need your queen to join up with the main attack. Make sure you funnel her towards the first 2 baby dragons. Then you get the advantage of her range, and she can take out enemy cc
6. Dropping bats in heavy fire. They only appear fairly slowly. So if you drop them in range of (for example), 2 x-bows, 2 air defences and an archer tower, you will be losing them as quickly as they appear. That is why you need to find a place where they can kind of congregate. Heavy HP defences that don't fight back (canons, mortars) are great, especially if the bats are out of range of any other defences. Always think of their route though. The later they reach wizard towers/multi-infernos, the more chance you have.
7. Dropping bats in different places. It's tempting at first to spam them all over the place. It just doesn't work. You will end up with 5 mildly damaged defences. They work as a team!
8. Not dropping your bats at all! This can be easily done. You often drop them on the edge of a village...if you're not careful, you try to drop 2 or 3 "out of bounds". It can be slightly depressing to realise you've still got 3 bat spells left and your whole army has been wiped out.
It's a fairly tricky attack at first, but once you get the idea of when to switch your whole attention to the bats, you will nail it. It's OP in MP, and pretty deadly in war. Enjoy!