YouTD

The potential of this tower is very hard to parse. At level 0 (which is never will be) it takes 7 casts to get every rune to 105 charge, at which point you enter a cycle of 3 random runes getting de-powered, 3 more, then 2 on the next cast. However at level 25 it only takes 4 casts to get over 100, at which point so long as the tower is casting, it maintains a near constant flow of buffs.
However that is offset by the limited range of 150, so it will only really hit towers directly around it.
5 seconds sounds like a reasonable duration, but the buff only is given off the back of a 40 mana cost ability that has to trigger several times. Assuming you had 40 mana every 3 seconds and level 25, you could consistently expect, for example, 25% attack damage, 25% attack speed, 25% trigger chance for 5 seconds every 16 seconds. But if you only generate 20 mana every 3 seconds, that buff only happens every 32 seconds.

Obviously it's ability to generate charges on attack can offset it, but that's still only about 20 charges about 1/3 the time.

When you consider something like Phantom, you can get a 50% attack speed boost with perks, and it only requires 15 mana to consistently provide the effect.

I think the tower is cool, but finding the specific balance point for tempo is hard.