At DForge's request, I've taken a look at this problem. In short, I don't think this is a bug. Here's why.
In his example, DForge wrote the following:
DForge said:
Turn 1:
Enemy shoots me
I shoot
Vic Shoots
Cassidy Shoots
Sulik shoots
Rest of enemies shoots
Cassidy shoots again
Sulik shoots again
Vic doesn't
Turn 2:
Normal sequence (enemy, me, team, etc.)
However, this is the wrong way to look at turns. There are four very simple rules to follow with regards to sequences and turns.
1) All critters in combat are ranked from highest to lowest according to the sequence. In case of ties, the order is randomized among all tied critters.
2) Whoever initiated the attack
ALWAYS goes first, regardless of its Sequence rating.
3) The rest of the critters (assuming the survived the initial attack) makes their move in the order of Sequence.
4) From turn two onwards, all critters go according to their sequence.
Therefore, in DForge's example, this should really be:
Turn 1:
Enemy shoots me
I shoot
Sulik shoots
Cassidy Shoots
Vic Shoots
Rest of enemies shoot
Turn 2:
I shoot again
Sulik shoots again
Cassidy shoots again
Vic doesn't shoot
Enemies shoot
Vic Shoots again (maybe during enemy sequencing)
Turn 3:
Repeat sequence in turn 2, accounting for survivors and Perception altering injuries/drugs.
This makes sense: A player character with 9 or 10 Perception is going to have 18-20 Sequence respectively. Stage 6 Sulik's sequence is 20, Stage 4 Cassidy's sequence is 18, and Stage 6 Vic's sequence is 16. This means that Sulik is always going to be faster than Cassidy, and Cassidy faster than Vic. Unfortunately, Vic is a little bit in trouble since some mid level enemies and almost all high level enemies have sequences of 16 or better. At 16, Vic's chances of going ahead of his mid-level enemies is randomized. And high level enemies (such as Floaters, Super Mutants, and Enclave Patrols to name a few examples) are almost always going to beat Vic in the sequencing game.
Also, just because a NPC can hit an enemy doesn't mean that he or she will attack it. The PartyAI also has a customized threat assessment routine for each party member. So it's possible that Cassidy assesses an enemy within range and the AI thinks that Cassidy can take it on, while Vic may assess the same enemy and decide to take on a weaker foe.
Hope this helps to clear up the issue.
Cheers,
-- The Haen.