Right observation, obviously this deploy is victim of barrage template, but we can observe that:
The first 2 infantry hit will be the ogryns, that can save at 3+. The leman russ, have their 4+ reinforced.
This two formation can sustain normal barrage, I think. Disrupt is insidious, but with a reorganization, can't cause some problem. Mw is letal if you are inside an house or in open terrain in the same manner for the infantry, about the tank, don't matter. Generally, infantry inside a cover are vulnerable in the same manner, the stands are side by side.
This deploy have function against tiranyd swarm mass engage. If there is a warlord titan near it, the advance will be great supported.
The use of this falanx is to move them in advance, in case of activation fail, move 15cm.
Is engage oriented. To receive or to do. Tyranid, LAtD, BL and Orks will arrive soon against the imperial line to engage, different for other armies, that I know, the Eldar. But if we think a classic long range combined assault of the eldar, (aspect warriors on wave serpent + autarch followed by one or two bike company, or something similar), this falanx can receive this assault and sell life dearly. Imagine a FF assault, classic eldar, and the first hit assigned at 3+ to the ogryns, or alternatively, 4+reinforced to the leman russ. In EA the assault make the difference.
The falanx in play.

here, receiving a tyranid assault.
