Friis law and the power delay profile
Basically, multipath propagation causes time dispersion (hence causing a delay spread ($\sigma_{\tau}$)) and that dispersion influences the fading characteristics of the wireless channel.So delay spread is related to the fading characteristics of a channel and not really to the path loss. Particularly, if $\sigma_{\tau}$ is greater than the symbol period ($T_s$) then the wireless channel is said to be frequency selective, meaning that a signal will interfere with itself causing additional fading.

You should also note that the rms delay spread is not the maximum delay that your signal experiences as I think you may asssume, $\sigma_{\tau}$ can be calculated as follows:

$\sigma_{\tau} = \sqrt{\overline{\tau ^2} - \overline{\tau} ^2}$

where

$$\overline{\tau} =  \frac{\Sigma P(\tau _i) \tau _i}{\Sigma P(\tau _i)},$$
$$\overline{\tau ^2} =  \frac{\Sigma P(\tau _i) \tau _i ^2}{\Sigma P(\tau _i)}$$
and $P(\tau _i)$ is the power of the component with delay $\tau _i$