No offense but I think it is the other way around. I didn't even include the hand payment thing. Since most times when I do even use them I only make 1 or 2 and it isn't hard to pay them normally. Personally I am too lazy to bother myself to get ready to pay them by hand since I am doing more important things then trying to catch a fast moving Reaper to save some money. And I only get them if I have access to Gems, otherwise it is not worth it unless its a short map.
Maybe it is just me, but I never had an encounter of slapping something on accident, I mean when the creature lights up when you scroll over them, that kind of gives it away what your looking at. I would suggest not spamming the slap button to whoever suffers this. Besides, even if you slap a Reaper it isn't the end of the world, if it is fully happy, it won't get mad, and even if it gets mad, it still isn't the end of the world. You can easily just pick him up and throw him in the Temple and he will calm down fast, or just drop him in the Treasury and give him a gift and all is better. He only goes crazy if you just let him stand still for like 5 seconds. Which is your own fault if your looking at him and do nothing.
I am actually surprised how you think people overexaggerate them when it isn't surprising at all seeing a single Reaper being able to beat down several creatures on its own easily. If you made a map where the enemy and you can get teh same creatures(Mistress and Bile Demon to name the important ones) But enemy got 20-25 creatures while you got only 10 BUT you could get a REaper or 2. Guess who is going to win? The one with Reapers since even at such odds they will tear through most creatures even at 10 in a few swipes.
Hell in some Deeper Dungeons a level 10 Reaper take out an entire Lord's party of all 10s by himself. Your talking a level 10 Knight, and usually like 2-5 others that are 10 and he can usually win or almost kill them all. And the Knight is meant to be the end of level boss.
Never said he can beat the Avatar but just look at Rex talking about their stats and they are pratically identical save the Avatar having another half as much health at base level and having some magic. So in your eyes the Reaper isn't OP even though he is almost on par with the Final Boss in the game? And yet if an Avatar is a unit to get it is too OP?
I mean your are free to think he is a good unit since he is, but it is hard to dispute him not being overpowered when this is a creature that is almost on par with the Avatar and you can easily get many of them on most maps.