In the spirit of addressing some infinite sustain (cheese-tanks), and adding another form of utility spell for support/sapper-based characters: Possibly reworking Force Siphon could help in this regard?

Also possibly giving a general skill to any healer for team dungeon sustain.

Force Siphon

Current:
Focus your staff's power to apply Minor Lifesteal to an enemy for 24 seconds, healing you and your allies for 600 Health every 1 second when damaging them.

Suggested:
Focus your staff's power on a target over 2s (Can be Interrupted). Upon completion deal [X] damage to the target's Magicka and Stamina, restoring a tenth of the amount to you and applying the Essence Thief Synergy on the target for 6s, whose interaction restores the same amount to allies. These values scale based off of the highest of your Weapon/Spell Damage.




The above is the largest point of consideration for this post, the morphs are more spitball:

Quick Siphon:
Current:
Focus your staff's power to apply Minor Lifesteal to an enemy for 30 seconds, healing you and your allies for 600 Health every 1 second when damaging them. When you or an ally hits the target, they gain Minor Expedition, which increases their Movement Speed by 15% for 4 seconds.

Suggested:
Focus your staff's power on a target over 2s (Can be Interrupted). Upon completion deal [X] damage to the target's Magicka and Stamina, restoring a tenth of the amount to you and applying the Essence Thief Synergy on the target for 6s, whose interaction restores the same amount to allies, and snaring the target by 50% for 4s. Grant yourself and any ally that interacts with the synergy Major and Minor expedition for 10s. These values scale based off of the highest of your Weapon/Spell Damage.

Adds Major and Minor Expedition to the caster and Synergy users, while snaring the target.


Siphon Spirit:
Current:
Focus your staff's power to apply Minor Lifesteal to an enemy for 30 seconds, healing you and your allies for 600 Health every 1 second when damaging them. Also applies Minor Magickasteal to the enemy for 30 seconds, causing you and your allies to restore 168 Magicka every 1 second when damaging them.

Suggested:
Focus your staff's power on a target over 2s (Can be Interrupted). Upon completion deal [X] damage to the target's Magicka and Stamina, restoring a tenth of the amount to you and applying the Essence Thief Synergy on the target for 6s, whose interaction restores the same amount to allies. You now apply Major Timidity on the Enemy, and grant yourself Major Heroism for 10s. These values scale based off of the highest of your Weapon/Spell Damage.