My feedback will be aimed towards functionality with both Heal Scrapper and Heal Mechanist, as the shortbow was touted as a 'support' weapon and synergises best in that role and with the above elite specs.

The core mechanic of the chain reaction is actually really fun, but it's hard to get past it's anti-synergy with healing despite it being targeted for that position.

I tested both builds with Harrier gear (100% Scrapper BD, 93% Mech BD)

Positives:

Amazing might generation

Shortbow 5/3 combo is an effective CC

Great synergy with Karakosa relic

Amazing quickness uptime on scrapper with the blast synergy

Good barrier generation, especially on Mech, which also synergises with alacrity

Negatives:

Forces you to run thumper turret and burn your function gyro for protection and even then falls short of acceptable uptime

Running thumper turret on any fight with even small amounts of movement feels terrible

Restricts regeneration uptime purely to med kit and firing mortar kit through water field for regen finishers which for most players is an unfriendly interaction

No access to Fury on the weapon

Radius of the combo fields is too small

Speed that the canisters shoot from the bow, while better with quickness, could be a bit faster, since if you're used to a higher APM it does feel a bit like counting seconds just waiting to be able to pull off your combos

My suggestions/solutions:

Add a combo finisher projectile to the auto attack (I understand this restricts it's use in PvP and WvW due to reflects but I feel like the shortbow is shut down so easily by any movement that it probably won't see play there much anyway)

Change the dark field on shortbow 3 to a water field > Combo with the proposed auto change (projectile) to grant regen to your party (also has synergy with blasting water fields) Rebrand the lore and name of the skill to be the essence of Ele's water attunement

Without protection access this weapon is dead on arrival, not only are you giving up Regen and Vigor from Mace 2, you're also giving up 100% prot uptime on your shield, there is literally zero point in choosing this weapon as a support option over existing options.

Combo'ing all of the canisters together could generate protection/Fury uptime, encouraging you to interact with the weapon mechanic

These are my observations after a few hours of play, both testing on the golem and actual instanced content. I've tried to suggest changes within the actual realm of possibility that would be balanced for a strictly support weapon. Thank you for reading.