I think Just removing the mining score bonus, and returning some of its mining speed would be a relatively good change. With the experience modifier nerf, coupled with the mining speed nerf and the basic clone bug fix, gauss abuse should be less prominent from Overload alone.

I'm not entirely on board with increasing the difficulty, however. My fear is that it will just lead back to the same overload defenses (single target) we already had, Sniper, venom, gauss etc. Towers like cannon and missile will probably never be seen in an overload due to them being projectiles and the fact that they deal aoe, while the enemies themselves are spread out.

The speed of the overload is added to the research, so the 15 overloads in version 1.8 are about 79.8 times the mining speed. Version 1.9 has not been tested and is estimated to be less than 20 times.

Overload was meant to allow the player to exchange some score with a bit higher difficulty, it was never designed to be used as the main source of mining speed boost.
The main drawback of Overload from 1.8.10 is the fact it will ruid your run almost immediately if you use it just a bit too much - and considering we have thousands of players which can not invest dozens of hours to replay a single level (and they don't want that), it is a massive problem.
My goals for Overload:

• It allows to increase your score a bit, it should not allow to get more than 50% score of the whole run even if you use all 10 charges, because if it does - it becomes a requirement which reduces the amount of possible strategies which allow you to get a similar, high score
• Ideally, it should not give you much more profit than using other abilities, because it uses an ability slot which can be used for something else. It should be possible to select some other ability instead of it, which should still be competitive vs overload
• It is aimed at increasing the score slightly, to be a slight push for your strategy, a last resort which allows to score a couple more points and break a tie in a competition with some other strategy that does not involve Overload

I don't mind if it increases the mining speed, but it must not be required to farm effectively. The lack of mining speed is compensated with x2.5-x4.5 resource multipliers on levels which should not be ignored if we speak about its reduced mining speed bonus.

And I don't even want to speak about the basic clone bug, it is called a bug for a reason. I'll repeat what I've said in that other issue - people like bugs which allow them to farm 100x faster or make their run last for another hour, but they can not be preserved, because they make everything else useless.
If there's a lack of mining speed or some other good old overpowered stuff, it should be carefully compensated with a new systems and mechanics that can be properly balanced and which look like an intended thing. Resource bonuses for levels do exactly that.

I'll take a look at Overload because I don't like its current version either, and its mining speed score multiplier is buggy for some reason.

Overload has been completely reworked in build 204. Closing this issue, please open it again if you find a new version of Overload poorly implemented