In 2018 and 2020 there were two buffs to make T3 units shields useful, especially 2018 one. It reduced time to recharge shields & overall regen rate.
Harbringer:
Shield Regen Rate:9-> 30
Shield Recharge Time:63-> 40
Titan:
Recharge Time:60-> 15
Regen Rate:9-> 20
Titan:
Recharge Time:15-> 12
Harbringer. :
ShieldRechargeTime:40-> 30
Both of this patches made Titans & Harbs have less health, but faster shield regen, thus upgrading more micro and versatile usage of units.
But there was no similar rebalance of Obsidian, which would perfectly fit him. Let's compare shield stats:
Unit: shield health/regen/recharge time
Obsid: 1500/+2 ./75
Titan: ...700/+20/12
Harb: 1000/+30/30
The obsidian has the strongest shield, yet the weakest regen. And so much so, that if obsidian's shield is damaged down to 10, it will take him 1490/2 = 745 seconds, more than 12 minutes to regenerate!
Recharge time is broken as well, since it buffs regen speed disproportionally. If unit's shield completely destroyed, it gets recharging instead of regenerating. And recharing is effectively faster per second than regenerating. Let's how much.
For Titan & Harb the difference between regen and recharge is not very big. 700/12 = +58.3 effective shield regen per second for TItan instead of +20, 2.9x times difference. 1000/30=33 effective shield regen per second for Harbringer, 1.1x times difference (small 10% bonus).
If obsidian's shield is destroyed completely, it gets fully replaced after 75 seconds. It means that shield recharge effectively gives obsidian 1500/75 = +20 regen per second instead of 2, 10x the difference!
So obsidian either need to get his shield destroyed completely to get a new one in a 75 seconds or wait more than 12 minutes for natural regen. It makes little sense for this unit to have a shield with current values, it could be just raw 2750 health unit.
I suggest to considerably buff shield regen for this unit. In order to not make it OP, up energy drain & reduce shield health:
Obsidian
Power Drain:10-> 25
Shield:1500-> 1200
Shield Regen Rate:2-> 12
Shield Recharge Time:75-> 60
This rebalance would also make Obsidian reflect overall game philosophy "save damaged units that have shields, they will regenerate quickly" we have in balance for a few years already.
Alternative proposition for Nomander (copied from Discord). Losing 300 HP is also too much so we can try to go for something that keeps its HP but makes the regen more comparable to recharge:
Shield Regen Rate:
2-> 9