Measured Numbers
Standardized gear (mid-investment, ~40 Divine) comparison: 0.4c Frostbolt CoC Blood Mage averaged 3,280,000 DPS vs Aldur. 0.5 version (triple Frost Resonance) averaged 3,190,000 DPS. Only 2.74% decrease, far below the community's feared 10%+. Reason: 10% cast speed partially compensates for 5% more damage loss, plus Frost Resonance's 12% more crit damage adds extra benefit.
Rune Configuration Advantage
Triple Frost Resonance (12% more crit damage + 20% stronger chill) synergizes perfectly with CoC: higher crit damage boosts each Ice Spear trigger, stronger chill provides additional defense.
Verdict
Blood Mage Frostbolt CoC is far from dead — it remains the strongest pinnacle boss killer. The nerf is negligible and does not affect its S-tier status. If you enjoy high-risk high-reward close-range spellcasting, Frostbolt CoC Blood Mage is still the ultimate 0.5 choice.