[Snake]

Electro Shield (Engineer) does not activate if the opponent uses skills/spells even if they are attacking with melee weapons. The only instance it activates is upon landing a basic hit with a melee weapon, which is inconsistent with the behavior of retaliation damage from other sources such as Armor of Nails or Fang-Faced Shield.

The skill should either clarify that it only works on basic attacks.

or

Be adjusted to work on all attacks regardless if it's a skill or not, BUT, only deal damage if the attacker is within 1 range of you. (So it doesn't undergo Dev Logic ™ like the two retaliate effects mentioned above.)

How to replicate:

- Use Electro Shield.
- Be damaged by a basic hit that uses a melee weapon.
>> Works! Lightning damage is taken.

-Use Electro Shield.
- Be damaged by a skill that uses a melee weapon.
>> Does not deal lightning damage...

- Use Electro Shield.
- Be damaged by a spell that uses a melee weapon.
>> Does not deal lightning damage... (However in this case it should be alright, I'm mostly concerned about skills that make contact with you yet ignore the effect)

[Autumn]

I swear I've brought this up before but this is because the effect is caused by a status, this is expected behavior from it and Enchant Shield. Where as the comparisons you are bringing up do not function fully similar, being item effects instead.

[Neus]

More of a balance fu than a bug report. Electro Shield is categorized as an on hit effect, so it only applies when a basic attack hits you.