Ram works such that if the attacker's Strength > target's Strength there is a probability for the target to be stunned; stuns seem to take the target out for approximately 1 minute of performing actions. While stunned they may still Avoid attacks or simply be missed but they will perform no attacks. Given the nature of the current game, beating some target's Strength will be very difficult; you have to weigh your opponents and get to be one Strength higher.
All tactics works such that a higher value increases the probability of using that tactic when it's "your turn" to attack; Strafe works such that not only does probability to use the tactic increase but the quantity of targets increases.
Not sure if Speed actually makes Avoid better nor occur more often - they just go well together as the Speed/Avoid combo has more hits and is more often missed in addition to the Avoids. Avoid works as a good complimentary, defensive tactic though. The 50xp per Avoid is nice, but it is better still when it can setup additional attacks that can lead to victories. For example, the Ram/Avoid combo is great in the Arena because it leads (a) winning, (b) more XP from avoids, (c) high Strength Ram overflow damage; at Level 2 there can be an average of 450 - 650xp from Arena fights (assuming Strength is high enough).
And of course,
repair is epic win with proper coordination.
More ramblings later...