In team fights, you will most of the time follow up a disable from an ally with Call Down and start attacking heroes with Flak Cannon with BKB activated. You don’t want to run in first because your opponents might simply disengage. If you waste your BKB and Flak Cannon duration you will be in trouble – the enemy team will be able to re-engage and your impact win the fight will be much, much lower.
What to keep in mind before a fight:
The most important thing to have in an engagement is your Flak Cannon. In case the spell is on CD, you should avoid fighting until it’s up. If you expect a fight to start soon, don’t use Flak Cannon to farm.
Your BKB is most of the time the 2nd important thing to have in fights. Provided it is on CD for some reason, you should also avoid fights, especially if enemies have strong burst damage or lockdown. If you need to fight but your BKB is unavailable you need to enter the fight only after your opponents use all of their important nukes and disables on an ally (ideally your tank/initiator).
Who you should focus:
Gyro is a unique carry hero in fights in the sense that he doesn’t need to worry about who to focus most of the time. The reason for that is Flak Cannon – you can attack anything that is in range and still apply damage to all enemies within a huge AoE. Because of this, you will deal the most possible damage by attacking your closest target, rather than chasing after a specific hero and wasting time.
In most situations, enemy carries will have BKB’s; this means that using the Missile on an enemy support will be the common choice (for example on a hero that needs to cast a lot of spells in a fight, especially if he/she has some channeling spells – Enigma’s Black Hole, Bane’s Fiend’s Grip, etc.). Using the Missile to disable a Linken’s is also possible.
How to move/survive in a fight:
As we mentioned already, Gyro is a relatively squishy hero even with BKB.
If enemy heroes start focusing you, you might have to move and kite them in order to stay alive. Keep in mind that the high range of Flak Cannon allows you to deal damage to enemies from afar. You can use that to your advantage, back down a bit to get away from the enemy damage dealers (especially strong man–fight heroes like Lifestealer, Ursa etc.) and attack creeps or enemy units that are close to you.
If the enemy man-fight hero doesn’t have BKB, Rocket Barrage (and possibly Aghanim’s) can help you deal enough damage to win the 1v1 hit exchange. Because of this, it is a good idea to try to position yourself away from other enemy units when fighting 1v1. In the earlier stages of the game, when the single target DPS of Rocket Barrage is still deadly even to farming heroes, you might even discourage a man-fight carry from focusing you just by activating Rocket Barrage.
In case you are winning the engagement, you can chase people down and finish them with Rocket Barrage (usually you will have good movement speed thanks to your items). You can also cast Homing Missile on running heroes to get them killed or at least to see the direction in which they are moving.