Short end: Encourage AP builds better, discourage Visage rushing at the very least (cannot remove the item from the champion, and that's fine), take away some power from the vast amounts of power is pool currently has.
I do think invulnerability should prevent both damage AND healing and not just damage. So basically invulnerability becomes like Kindred's ultimate, whether it be a Kayle ult, Taric ult, Bard ult, or Hourglass active. This would help balance out champions like Swain and Vladimir better so they aren't invincible AND healing from it too, and then revisit them if a change like this makes them too weak.
Heal: 0(+30%AP) [from 20/25/30/35/40(+15%AP)]
Enhanced Heal: 40-240 based on level plus 6% per 100AP missing health [from 40-240 based on level plus 5%(+4% per 100AP) missing health]
Crimson Rush: Duration down to 1.5 seconds [from 2.5]
Movement Speed: Up to 20% for 1.5 seconds [from 10% for 0.5 second]
**Sanguine Pool (W):**
Movement Speed: Removed [currently grants 37.5% decaying movement speed over 1 second; already grants him untargetability, slow, damage, damage-to-healing, and keeps his mobility so he doesn't need movement speed with his pool]
**Tides of Blood (E):**
Damage: Removing 30/45/60/75/90 to 60/90/120/150/180 (based on charge time) base damage
Cost and Ratio: Health to 2% to 8% max health (based on charge time) plus 70% ability power
To Replace Base Damage: Tides of Blood deals 30/40/50/60/70% increased damage if fully charged