This is, of course, wonderful... but does it make sense to free up an entire slot (or several) for Master Djinns??? especially just for one or two??
I don't know about you, but I don't split my army too much, especially if I don't know the enemy's location and strength. At whose expense would I add Djinns to the army? At the expense of the Goblins? - maybe... well, you could also remove some Gargoyles if there aren't many. However, if there hasn't been a major unforeseen loss, it's unlikely that there will be few Gargoyles and Goblins at the beginning of the 2nd month, when you can already start scouting with a strong force. Let's assume that by the beginning of the 5th week, there haven't been any major losses... everything has been built and upgraded to level 7 (although achieving 200% is difficult). We gather an army to break through to the enemy. Who should we remove to free up a slot for the Djinns? There will probably be at least 150-200 Goblins (units). With the castle's parapet, there will probably be 80-100 Gargoyles as well. To streamline the army, it's better to remove the Goblins – then we lose a ranged unit, which is important when sieging a castle (besides, they distract the enemy's towers and archers). Who will the tower archers shoot at? - most likely at the mages!!! And are you not sorry to lose them? -)))) If you remove the Gargoyles, you lose meat shields, and there are quite a few of them, which can withstand enemy attacks (besides, they are flying meat shields))... I don't see the point in splitting them up!
The main thing is that you can't predict which spell the Djinns will cast... this is probably only good with a clearly strong army and without serious battles with sieges and losses.