TLDR:Changes to:Song of Discord: Very little impact. Song of Resurgence: High impact, healing much reduced. Song twisting: much reduced value. Build still very viable for GK.

Testing was conducted in GK by soloing the patrols & whilst in a 4-person group that downed the Egg/ Clutch boss on level 2 i.e a high-geared group.
Skills used were Bard /Druid (Double Song build)
Gear used max. crafted with augments (58 mods). No gear had been altered since the patch.

Patrols were still able to be soloed one-on-one, but fighting 2 at once still meant death i.e. no change. However, the margin of error has been much reduced (See below).
Group work required extensive use of Druid healing spells as Song of Resurgence healing was much reduced

Song of Discord:
Base damage = 309.1 /2 seconds AOE (9+mods fitted).
During fighting typically ticked for 400+, saw it peak at 514. Before patch had seen peaks of 700+
No real impact from changes, damage was sufficient to kill patrols

Song of Resolve:
Base Heal = 35 AOE + 20 to Self /4 seconds (2 mods fitted)
During fighting typically ticked for 70, peaked at 90+. Before patch had seen peaks of 400+
Changes to healing had a large negative impact (that was replaced by using Druid spells).
Song twisting (swapping between Discord and Resurgence) had much reduced impact