Scouts (sentinels here) are generally used to form a protective shield by placing their ZoC over the target while staying out of intermingling range. The point of this being that you may not enter (or land in) the ZoC of any formation that you are not assaulting. Remember that the sequence is activate, declare intermingled then move (and barge etc), so you cannot 'barge' the scouts into the target and then declare them all intermingled.

The normal way around this is to use another formation to break the screen, then assault the target. So teleport Terminators in to shoot / assault, then THawk to assault the target, then further THawk(s) to recover assault troops.

A riskier alternative is to use the THawk assault to clear the screen (regrouping the ground troops afterwards) then use the second THawk to assault the target while embarking the ground troops. If you are able to avoid AA on the way in and given that the target has picked up a BM for supporting the earlier assault together with kills, you could go into the assault +2 or +3 which is usually sufficient to win the assault against small Artillery targets (3 strength). If in doubt, you could leave the Assault marines outside for additional support as they can then double to support the next assault (and get picked up etc)

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"Play up and play the game"

Vitai lampada
Sir Hemry Newbolt