Firstly, attacking zero def targets is going to do diddly squat for your hopes of finding a Demi God, it's been that way for years.
Attacks made while in tournaments will do diddly squat for finding Demi's, you cannot find a Demi while in a tournament, period. (Although you can be awarded one depending on how well you do, and what type of tournament you are playing)
A number of different factors go in to deciding if an attack is eligible for finding a Demi God, note, eligible, not 'will give a request'. The simple rule is, to find Demi gods, you need to attack people with defences built. If you attack somebody who has a very similar defence power to your attack power, you will have the best chance of getting a request as the system judges you having a 'fair fight'. Note: In this case, Bigger is Better, higher the stats, more chance of requests.
You will be told if the attach was eligible, a summary is at the bottom of your attack log. Each eligible attack has a small percentage chance of resulting in a Demi request being sent to you. Each attack is a separate role, and it takes not account of the number of failed 'chances' you have already made. So, the chance 1 attack results in a Demi, is the same as 10 20 or 100 attacks (each has the same chance).
The percentage chance for finding a Demi can be affected by a number of things, firstly for each Demi God you already have (not including the self Demi) will reduce the chance of finding another. Second, you can increase the chance of finding a Demi, by building M2 stargates, the increase is slight, but it is an increase all the same.
Do not expect to find Demi's like candy, but you should expect to find at least one, for every 3k eligible attacks you make (give or take) depending on the above.
Demi's are supposed to be a little extra flavour, not massively effecting the game. Ofc there are a few exceptions, like the super weapon Demi's and the ones that grant additional turns per turn change, but 99% of them just add tiny little tweaks.
So in short, find a target with similar stats, and mass em


