If I cast Gust targeting a 2 Might unit in response to a Quickdraw trigger (before Sterak's attaches and would make it 5 Might), is Gust legal and does it resolve?

Ruling: Yes, Gust is legal and resolves. When you cast Gust in response to the Quickdraw trigger, Gust resolves first before Sterak's attaches, so the unit is still 2 Might when Gust checks its target validity.

Sequence:

• Sterak's is played from hand
• Quickdraw trigger goes on the stack
• Gust is cast in response to the Quickdraw trigger
• Gust resolves while unit is still 2 Might
• Quickdraw trigger resolves and Sterak's attaches

Nuances:

• You cannot react to Sterak's being played itself, but you can react to the Quickdraw trigger