From a PvE perspective, 3 skill lines in particular see almost no use in any role. They are:
1. Draconic Power
2. Shadow
3. Dark Magic
While they see some usage in PvP, they serve almost no niche in PvE. Here’s why:
1. Draconic Power. This skill line is currently designed to offer a ton of survivability tools for tanking, which isn’t actually bad. However, tank meta in ESO really focuses on being a source of buffs and debuffs for the group, and Draconic Power is entirely selfish. I would like to see something on this skill line that would fix that, and provide group utility rather than just selfish survivability.
2. Shadow. This skill line suffers for 2 reasons: it’s too selfish for tanking (similar to Draconic Power) and it’s too weak for damage dealing. To make it more viable for tanking, add useful group buffs (such as AoE minor berserk on Shadow Image or something). To make it more viable for damage dealing, give Twisting Path a synergy (like Lightning flood). Also, Shadowy disguise cannot be used with some abilities due to restrictions around invisibility. While that’s likely necessary, I would like to be able to get the 10% dmg done to monsters even if the invisibility fails. Let the skill cast, but the invisibility portion fail, if possible.
3. Dark Magic. This skill line wants to be pure utility, which is why it still sees a bit of usage in PvP. However, there’s no real niche for that type of utility in PvE meta. To fix this, I propose adding some damage utility to some of the skills. Let both morphs of Crystal Shard provide an armor debuff. Let Rune Cage provide a unique damage buff (like Stone Giant’s Stagger). Sorcerers have had a place in PvE meta as buff bots for a long time, and I think this skill line should play into that.
These are just suggestions, and the important thing I want to emphasize is why these skill lines all fail: they are selfish. They need to contribute to the group, through either buffs or more damage, to catch up with other options available via subclassing