How to reproduce:
1. Download attached project and open the LightVolumes.unity scene
2. Let light baking finish
3. Press play
4. Observe batch count in 'stats' window and/or check generated batches in Frame Debugger

Actual result: Dynamic objects lit by a Light Probe Proxy Volume do not dynamically batch together. In 2017.1.0f3 and earlier versions, this used to work.

2017.1.0f3: Batches 9 (saved by batching 30)
2017.1.3p1 Batches 29 (saved by batching 9)

Note that the 'saved by batching' in 2017.1.3 is all static batching. Looking at the frame debugger shows no dynamic batching occurring in the test scene.

Reproduced with: 2017.1.3p1, 2017.2.1p3, 2017.3.1p1, 2018.1.0b7
Not reproduced with: 2017.1.1f1, 2017.2.0b8

Regression since: 2017.1.1p1, 2017.2.0b9

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By Design: We don't support instancing/batching for LPPVs. LPPVs still need normal SH / object to evaluate L2 band. By mistake, L2 band coefficient were not set before and the result lighting was wrong. It wasn't breaking the batches before because L2 coefficients were the same(0) for all the objects that were using LPPVs.