Irregular tomestone grinding efficiency

[Ryphen]

never payed any attention how long pvp matsches last but don't the last like 12+ minutes at least?

Generally, yes. Shatter and Seize usually last in the neighborhood of 12 mins. Secure is more variable, and it's not uncommon for it to go over 15 mins. Hidden Gorge can be anything from 5 mins to full time. I don't think there's any way to play 15 matches in an hour unless the other team(s) are virtually afk the entire game.