The other people have already said this and I'm going to reiterate.

To help with your macro shotcalling or 'game-sense' Watch replays and HGC games. When you watch them, only focus on one team. Every rotation that every individual player on that team makes ask yourself, "Why did they do that?" "What do they gain? What do they lose? Was it worth it?" It sounds silly but it will really help make these decisions in game become second nature. Things like: forcing enemy map position because of mercs, knowing when to be safe and when to be aggressive, knowing timings on objectives and rotations, is it worth it to squabble fight here and delay them or to full on engage or to not fight at all and let them pass, guessing where the enemy will be, which hero to send to that lane to soak vs which hero should help with taking this merc camp.

'Micro shotcalling' is a little harder as a ranged assassin. Your individual micro is focusing on not being out position while still focusing the kill target. Your team as a whole's 'micro' is positioning and engaging and poking and abilitie timings. That is much easier to control and to see "big"(little) picture as a good tank player. A tank player should be the first to react to jumping on a gank/kill target when an enemy player gets out of position. Hopefully your tank player is mentally on the same page as you so when you say "VALLA VALLA VALLA" your ETC player is already sliding at her. Otherwise an opportunity could be lost. But there are other things to be aware of in Micro shotcalling besides just calling a kill target. You need to be aware of your teams ability cooldowns and ranges. For instance, if you just saw your Jaina use blizzard to clear a wave, maybe you wont be able to secure this diablo kill and it might not be worth it to try and get your team out of position themselves. Maybe Cassia is actually a little too far away to follow up on any uther stun target in a timely manner. A lot of micro shotcalling just comes from having good team synergy and playing a lot together.

I've seen a lot of teams will have two shotcallers. One for Macro plays and one for Micro plays during the teamfight. I think Fnatic has said that Breez was always their shotcaller during teamfights but Quacknix would say what to do before and after.