I feel Luden echo is way out of hands

The main problem with luden echo is the Base damage of 100. The ap ratio is fine but the base damage is ridiculous. Champion with combo can proc luden echo twice in a row. Lets give an exemple on leblanc. Each abilities give luden echo 20 stacks. What if Leblanc has 100 Stacks at the beginning? She would:

Q (Proc luden echo), R(+20), W (+20), E (+20) While the champion is chained she can move gaining stacks + 1 per steps. and by that her Q would be up for another Luden Echo Proc

Dealing a total of : 100+100+ 30% Luden echo damage :O

Katarina same thing if she gets a single reset, God the humanity on her Luden Echo Proc. If done correctly she can proc it like 5 times for a total of 500+75%, is that a bit too much?

Casseopiea is the same problem by spamming E while moving Luden Echo will constantly proc + her Q W R making it ridiculous. Not only that Cass movmenet speed after hitting Q help stacking luden EVEN MORE.

Champion that should have benefit from luden echo does seems to make much out of that item. Because of terrible low cooldown on mostly W E and terrible movement speed.