Minefield support is penalising throwing speed too much

Minefield support at level 20 reduces throwing speed by 60% and grant 5 thrown mines per skill use. It would be expected that this increases throwing rate by 100%.

With increased 37% mine throwing it takes 2.63 seconds to throw 15 mines without minefield support.

With increased 37% mine throwing it takes 2.0 seconds to throw 15 mines with minefield support.

This is an increase of only 30% rather than 100%.