depends on the Talent. if you use Focus on a Tome based Minion Build, Focus would also increase the damage of Summon and Command, same as for Barrage and Twister, for example.
Now thats pretty good .
Just achieved the holy summons grail in pvp. During the match i got 12 furies and 2 spirits. Lol
It was a 2v2 match. 6 furies per character seems to be the max you can be lucky enough to spawn. You have to have a lot of hp and regen for the chance to occur at all. Armour may contribute. Perhaps. But summons are fun but not so fun if they belong to the enemy