W/D/W as it eventually became, that is with zero dry in the wet cabs, is often fairly simple. It doesn´t lend itself very well to the cascading series-parallel FX units of the big stereo rigs, since the routing becomes a big headache without the dry signal coming out at the end and you end up feeding FX only with FX. All the huge pro W/D/W rigs from the very late 80s and 90s had dry in the wet cabs; EVH, Lukather, Landau and so on. They just stuck a dry cab to their existing stereo rigs and called it a day. This would be refined later when the demand for that FX-heavy sound lessened.