The DRL circuit in the RAV4.3 is somewhat like both high beam paths in series due to the normally closed configuration of DRL No. 3 Relay. When the halogen bulbs are in place, they act like resistors in series, so the 12V power gets reduced at each bulb, and there's less intensity.When I installed the other 9005 LED in the high beam, neither came on as DRLs. So I'm sure you're onto something about the wattage being used to power everything.
Just like any electronics, LED drivers need to have the proper voltage to turn on, but LED intensity is controlled by current flow, not voltage. Thus, some LED "bulbs" out there won't work as DRL or could work, but with flickering since their drivers are trying to compensate for the lower voltage.