The main problem that I find with this monster is that it is too unbalanced. 
You need to launch many attacks where you will not have any help, because this monster does not attack you or at least I haven't interacted with him enough to believe it.
To attack it you must do many deliveries. The better score I can see in my club is 80 or 120 deliveries per war, but war last 2 days, so you have plenty of time to do deliveries. Those really active player who makes more than 120 deliveries per war, still can't launch many attacks to this monster, because you only can attack this with 4 types of disaster, that means for those 120 items probably only 50-70 are useful for those attacks, so you need to change some deliveries, and wait 5 minutes everytime you do that, then, this monster leaves in hours, not days! you only have some hours to reach 120 deliveries? not achieveable.
This without naming the lousy prize at the end which is like a bucket of cold water to the face.
The statistics they used to create this new feature is far enough from reality, as a real player you can't do much, even if I wanted to (this is the other problem, we don't even try because we know rewards are really bad), it is too difficult for me to defeat this monster unless I ask my clubmates for all the war items they have, or compete in an '' open war '' with another club just to kill the monster of my city, too much for so little.
but yes, it has a solution, fixing the numbers a little: 
1. The monster may attack you from time to time, to give you some items that you can start with.
2. Something more entertaining, beyond getting the chests, another thing that excites the players a little more, having their own season or tiers per month, so you can try to defeat many monster to unlock tiers and get better rewards.
3. Even that, improve the chests they give, 5 gold keys is laughable, or 1 rock monster card, come on... 
4. The time needs to be fixed, those monster leaves too fast. 
5. Heatlh is still to high, It is boring to beat such a tough monster individually, where there is no team club or you don't receive items because he attacks you again.
6. I have to say this: remove those COM tasks about war, stop overwhelming the COM.