MP,
With the 8 ohm resistors gone, there is no voltage divider. The pull-down resistors turn-off the output transistors and discharge capacitances, when the driver transistors turn-off. Without pull-down resistors, the bases of the output transistors gradually (as their capacitances slowly discharge though their leakage) "float" down to a voltage level that is determined by their substantial leakage current (which increases with temperature) and so the output transistors don't completely turn-off.
The Zapco PSU schematic is in Reply #28, and shows 4 paralleled transistors on each side, without emitter resistors.
Ante,
Zapco either matched the paralleled transistors, or had good luck.
Think of emitter resistors as a form of negative feedback. When a high-gain transistor attempts to conduct a large collector current, then that current creates a voltage-drop across the emitter resistor, which reduces the base-emitter voltage and therefore reduces base-drive.
A transistor with less gain will attempt to conduct less current and therefore will have less base-drive reduction. So the gains of the transistors are equalized.
Without emitter resistors, when a high-gain transistor is paralleled with a low-gain one, then the high-gain transistor will conduct more current than the low-gain one, which results in unbalanced current sharing. Without balanced sharing, the high-gain transistor may exceed its maximum current and/or thermal rating and blow-up.
