I mean, a 90% buff to stone golems regen is only like 90 flat regen, I dont think thats super crazy or anything.

 

also I think your ziggy math is wrong, when multiplying the base damage with the increased damage I think you multiplied it by 3 and forgot to carry over the base damage of the degen and used only the damage that the increased damage gave you for the rest of the calculation meaning you missed out on 4000 base damage which is a ton. Basically you did (((4000x3)x1.49)x1.59)=28429.2 which is wrong because you dont multiply by 3, you multiply by 4 since you need to carry over a 1 since the 1 represents the base damage like you did for the rest of the calculations (1.49 for 49% it should be 4 for 300% to carry over the base)

I think the number you were looking for in the calculations was(((4000x4)x1.49)x1.59)=37905.6

 

Also I think that controlled destruction would apply to the degen cloud because it says in the wiki that any minion modifiers apply to the caustic cloud and golems count as spells which gives you another 44% more damage multiplier. Your spell echo should also be giving you that 10% less damage multipler and since your degen is actually a huge part of your damage it might actually improve your damage to drop spell echo, not sure really how worth the 90% increased flame golem damage for 8 seconds compaired to 10% less on the degen, it might be better to use spell echo for pack clearing though. Thats something that would need live testing to know how it feels.

 

Lastly, if you wanted to do a shaper kill with the build then you could swap in chaos golem for the chaos tag to be able to use Void Manipulation for another more multipler and for your 6l you can use Chaos Golem/controlled/void/conc/minion damage/minion life for max degen. I think it would give about a 105k degen if I assume that the chaos golem will have about 55k life (im just guessing the life since you said your flame golems have 40k life and chaos golems are generally much tankier. I might be over estimating it though but I think thats a realistic amount of HP for a chaos golem if I use your flame golem as a base.