If a person uses Barrage of Rockets and then Frigid Touch on my Yone Blademaster, does it kill it?

Yes, your Yone, Blademaster will be killed.

Analysis

To determine if a unit is killed, we look at Rule 428.1.a.2 (Passive Kill) and the Lethal Damage Modification FAQ: A unit is killed if it has non-zero damage marked on it that is greater than or equal to its current Might.

Sequence of Events:

1. Rocket Barrage: Once the effect resolves, Yone has 4 damage marked on him. Because his Might is greater than 4, he is not killed at this moment.
2. Frigid Touch: This effect reduces Yone's Might by 2.
3. Resulting State: Yone’s Might is reduced to 3.
4. Check for Death: Because Yone has 4 damage marked on him and his current Might is 3, the damage exceeds his Might.

Conclusion

Yes, your Yone, Blademaster will be killed.

Under this game state, he has 4 damage marked on him and his reduced Might is 3. Since the damage marked is greater than his current Might, he meets the criteria for a Passive Kill per Rule 428.1.a.2.

Note: I could not fully verify this ruling against the retrieved rules.