Path of Exile explains upcoming Energy Shield mechanical changes

There are some big changes coming to Energy Shield in Path of Exile’s next expansion, and as tends to happen with major system changes, the designers have penned a lengthy column explaining why these changes exist. It’s not that Energy Shield is inherently bad, obviously; the problem is that with high enough values and the right collection of relics, players can ultimately use Energy Shield to completely replace Life as a survival mechanic, which results in characters with enormous health pools without any investment in doing so.

To fix this problem high-end shield values have been significantly tuned down, and several different items have had their synergy with Energy Shield adjusted to provide a more tangible drawback. Vaal Pact, for example, will no longer provide any benefit to Energy Shield (whereas it currently allows almost an immediate refill of shields without any drawbacks). However, it will also be possible for players to craft better Energy Shield items earlier, so players can still try out the builds that made these changes necessary; they’ll still be potent, but they should no longer make you effectively unkillable.