Immortal will make Fernando invincible, even to Dragon Punch. If he's hit, Drogoz will put Fernando down to 1500 health, and Dragon Punch will be cancelled.
Salvo does insane damage to your shield. Wait for Drogoz to use his Salvo before pulling it out. If his team is not focusing you, you might save your shield if they decide to push.
If Fernando doesn't have his shield up, try to hit him with your spit (don't detonate it). After it hits, you do more damage to him with your rockets, taking him down faster.
When Fernando activate his Ultimate to counter yours, try to aim for his teammates that is not in the Immortal radius. This way you wouldn't waste your Ultimate.