Gargoyles work better if your base has lot of chokepoints, so in the moment they see the enemy they can also overpass the path and it’s good because are the only unit that can do this. But the consequence if you put only gargoyles in your waves is that you run out of units and you give only time to the opposite king to regenerate the health since no enemies are coming against you.
Many spells can one-shot max gargoyle if leveled up at the right level, the first spell come in my mind is that Blizzard lvl 7 can one-shot Gargoyle lvl 4, however becauser of its cooldown, it’s not good use it in a base where there are lot of waves full of gargoyles.
Then we have Hammerstrike as primary spell it works perfect also against gargoyles only that in this case because of its low range, you have to wait almost that gargoyle are going to kill you and if you don’t have practise with time it’s better avoid to use it hammerstrike even if it can kill them in one-shot.
I suggest also Stun because thanks to its daze effect you have the time to kill 1 by one or let your troops kill them all without so much problem. But pay attention to its cooldown: 20s are infinity in this situation so i wouldn’t suggest it even if it give you the time to kill.
Swordrain very efficient and very cheap probably around lvl 7-8 can kill out these annoying gargoyles. However its cooldown of 15s isn’t the best in the game.
Same thing for Bladestorm: very slow and if not upgraded at the right level it won’t kill them immediately since it isn’t a instant spell but a “Touch & Go” spell genre.
Sonic Blast very similar as Bladestorm but works better, but the rule is the same: "low level > more time to kill gargoyles; high level > less time to kill gargoyles since that they can kill them before they do the final animation ! So you need only to cast the spell as you see that gargoyles are approaching you and say goodbye to them !
To sum up in a base like that where you don’t have time to cast continuously spells next spells, i would suggest you 2 instant spell like Hammerstrike and Blizzard. The first because it has low cooldown so you should have more time to kill “non-stop” those gargoyles, the second to use if you see already them cast it before they reach you since it has high range ! (and also you can slowdown them if you don’t kill them in 1 shot, so it’s perfect !)
Instead for defence i wouldn’t suggest to put only gargoyle even if that guy used mostly them in its waves, because as you said once they will die, they create a huge gap between one wave to one other, so if you really want to put gargoyle in your waves (because at that level are extremely powerful and good to use) i would put 3 gargoyles, 1 froster and something else of range troops. in this way after that gargoyles will die at least the range troops won’t die thanks to its range and they will block if possible, the regeneration of king and they will be able to kill your troops.
Paladins are good at low-mid levels gameplay, then even if boosted they lose its strenght because there are others troops/spells enough good to take down an army in few seconds than use those paladins. They are good at low-mid levels gameplay because in that period your king isn’t able to kill them immediately for various reasons: low level of spells, low level of troops, low level of your attack of Hero, etc. So thanks to its high health they can block you enough to lose lot of time like a Surprise Mummy could do for a high-level player.
In my opinion let’s say that paladins and boosted paladins for low-mid levels are the equivalent of lot of mummies (better elite mummy) put together. I lost me too lot of time long time ago against paladins when i was at your level and they are extremely annoying especially if elite boosted, now even if boosted its low “health rate regeneration” doesn’t work properly so they lose they usefulness and from that moment is better replace them with some other troops which work better.
However for low-mid gameplay you won’t find hard skull towers to defeat so paladins which have blunt resistence will fight better and resist better. but high level of skulls towers can crush them immediately althought their resistence, so once again better the replacement.
Hope this little advices can help you to improve your defence and attack side !
Thanks for understanding.