Just throwing out an idea of a potential way to make gameplay involving spirits more interesting.
One change I’d like to see regardless is that as well as a buff on the player showing when the effect is available that the spirit lights up and the corresponding icon appears above the spirit. It should help visibility and less having to look at the buff-bar.
In GW1 spirits/nature rituals had a neat mechanic of affecting all targets in range (allies and enemies), it was something to build around but usually a bit gimmicky. Hilariously powerful effects like EoE are off the tables, but if the spirits in GW2 were redesigned to respond to either an action from the enemy or the ranger/ally that could be interesting.
For example, with Sun Spirit if every 10 secs the spirit could either a) if an enemy applies burning to the ranger or an ally, the burning effect applied is copied (not removed) back to the enemy OR b) if the ranger or an ally applies burning to an enemy the spirit copies the burning to nearby enemies. Give the spirit a cast time (1s) for either effect so there is time to cleanse the burning or interrupt the spirit or dodge or waste the effect with a short duration burn, so it is a more powerful effect but can be avoided.
For other spirits it is important that the effects trigger on different actions to make spirits more interesting, as well as a unique ‘copy’ mechanic:
Frost Spirit: Copies ‘chill’ back at an enemy, or applies frost aura (the version with 10% damage reduction) to an ally that gets crippled/immobilised.
Stone Spirit: Copies ‘stability’ to an ally when applied by an enemy, or applies ‘protection’ when an ally is stunned or knocked down.
Storm Spirit: Copies ‘fury’ to an ally when applied by an enemy, or casts ‘swiftness’ on an ally when they crits a target.
Water Spirit: Copies ‘regeneration’ to an ally when applied by an enemy, or when an ally dodges heal nearby allies at end of dodge roll.
Frost Spirits damage increase should be a baseline function of all spirits or an adept in nature magic, whenever a spirits triggered effect is used nearby allies get the damage boost, Fire/Storm/Water should be easiest to trigger.
One additional mechanic is that while a spirit is ready to trigger it’s effect and the activated skill is used, then this consumes the triggerable effect as well as boosting the activated effect e.g. solar flare on the sun spirit gets an additional pulse of blind. So there is more choices to make when using spirits.