No more than 5 Minor Actions at the start of your turn. Wired 4 (or whatever) puts you at 1 Major 6 Minor, presumably you'd be allowed to convert 4 Minor to a Major "Before" your turn, otherwise Return on Initiative investment (Minor actions anyway) would be capped at one level lower than what most of them go up to. 2 Major, 2 Minor should be able to pull it off.
And if your GM says "No", just pull out Indirect Iggy. Just a guy. In normal clothes. Totally just standing there. With Focused Concentration 3 sustaining 2 Increase Attributes and Increased Reflexes with 3 net hits. Toss an Amped up Blast Spell (Base Drain 4, Amp up Damage, Increase Radius by 4, total Drain 8, Base Damage to target 4 plus Net Hits). Then do it again with your second Major Action. And stand there and see if anyone makes the Perception Threshold 6 test to notice you cast two spells. "Windy today ain't it fellas?" Mage will likely take 4 ish stun damage. Magic 6, Spellcasting (Combat) 6, so 14 Dice vs Reaction plus Willpower to everything in a 6 Meter Radius. If the Mage is Hermetic they'll have picked up their 2 Edge for the turn with Analytical Mind.
The Mages damage potential will increase more than the Samurai once play starts. Bond a Foci for 4 more dice with Combat Spells, potentially increase Magic to 7 down the road for another +1 DV. The Mage and the Samurai can both pick up one more dice on the Attack with Expertise. Also possible to pick up another Dice initially with Aptitude (Skill) Quality.
Doing a Drekton of damage to multiple targets at the top of the round is a pretty minor investment for a mage. To the point where it's just arguably a just side effect of normal optimization. A Samurai has to build their entire character around it, and it's pretty much their bit.
Edit: Oh, yeah and the Mage can just do it again next turn. Although you'll really need a nap if you keep Amping up the damage.