I can elaborate, but I think this will say a lot:
With the bosses mana being so slow it was easy to re-charge my Pixies in time and shut them down - I don’t recall any boss firing on this stage, so actually Shrubbear wasn’t needed here.
Also, with the ability to charge up mana in advance of the boss stage it was trivially easy to build up a minion shield from Kvasir. That’s a TON of extra hit points.
One general point I’d make about this team is that while they’re three star heroes, the effects of mana control and minion production are extremely powerful and more common to higher star level heroes. It may more appropriate to think of this as a three star team with four star effects.