About the additional axe thrown by putting sidearm rune on the frenzy skill

Question

The skill description makes it seem to as if frenzy runed with sidearm will give a 25% chance of throwing a piercing axe on top of the attack. Is this true or am I misunderstanding something?

Example of what I mean: Assume I am fighting one single enemy. If the piercing axe procs, will that attack deal 220% weapon damage to my enemy (110% from the normal attack and 110% from the piercing axe)?

If this is true, then what is the point of the maniac rune? The maniac rune will boost dps by an additional 20% of weapon damage (but only when at full frenzy stacks). But the sidearm rune boosts dps by 25% of weapon damage (and is not dependent on having full frenzy stacks).

Answer 1

My understanding of it as far as how the pure Frenzy damage works out matches yours.

However, I can answer why you might want to use Maniac. One reason is that the 20% damage bonus you build up applies to all attacks, not just the Frenzied attacks. Therefore, if you've built up the 20% damage mod, it will apply to things like Leap damage, Revenge damage, etc. Adding 20% to AOE attacks can be very nice.

Furthermore, one unfortunate side effect of Sidearm that caused me to stop using it is that when I'm working my way through Act 2 Inferno and have to be very choosy about my targets, sometimes shots go flying off at people I don't want to hit. In particular, it's really annoying for a Sidearm shot to fly off and set a treasure goblin running while you're still dealing with other mobs.