As someone who designs circuit boards professionally, the explanation is clearly lacking. There might be a thermal issue or there might not be. There is nothing conclusive in the pictures either way. What I do see is the following:
1. Underfill (the brownish-tan smooth material surrounding the components towards the bottom of the picture) around the IC, which is typically done to make parts more mechanically robust.
2. No evidence of overheating on any of the thermal interface material that is left stuck to most of the components and no evidence of overheating on the PCB or the components themselves.
3. Completely insufficient evidence to declare a soldering issue. The way to prove this one way or another is x-ray inspection to look for voids in the solder or a mechanical cross-section of the suspect solder joints.
While this certainly could actually be the problem, I see insufficient evidence to conclude one way or another. Manufacturers don’t put underfill under a part unless it’s required through testing or experience with similar package types in prior designs since it adds cost, additional process steps and makes it a PITA or impossible to rework any bad components in the area.
As to the pad size/shape, there are three general classes of design defined by the IPC (standards body that deals with PCBs and PCB assemblies). Depending on how space constrained your design is, there are different recommended pad designs for passive components like these. They might be using one of the tighter spacing guidelines, but if their process is well controlled, it can be perfectly fine for the design life of the product.
If you want to see small pad layouts done well, look at an iPhone logic board.
If you want to know more about pad design for SMT parts, search for IPC-7352