There are several points to note here.
- Counter-charging is optional; the defending unit(s) do not have to move and need not use their full movement.
- Counter-charging is evaluated on a unit by unit basis, with each moving towards the enemy unit nearst that defender. This can force defenders to move in different directions.
- Counter-charging is deemed to be a "move"; so embarked troops may dismount and units in the formation must be in coherency after the counter-charge.
- War engines may 'barge' during their counter-charge.
While this may sound a little goofy, it represents the situation where several formations are firing and moving towards a defender, which is in turn moving to meet the most critical threats or being pinned in place by the various attackers.
The usual tactic is for the attacker to move a supporting formation up to one side of the target and then have a second formation perform a clipping attack from a different direction resulting in the defenders being 'pinned' by the supporting formation and unable to move without losing coherency.
However in the situation you describe it is quite possible for the Titan to counter-charge away from the assaulting formation and end up outside 15cm from any of the assaulters in which case the assault fizzles out altogether. In really extreme cases, if the supporters were >10cm from the Revenant, it could end in B-B with the supporters and fight the assault with them instead of the original attackers.