Example: Me and my buddy are warriors and we both use "WATCH YOURSELF".
Question: Does the two abilities together provide +40 or just +20 from one of them? Question: How significant is +20 AL? Is the tactic skill even worth using for PvE?
=T So for me to get the +20 bonus, I would need to have someone else next to me use the ability? Hmm.. +20 bonus, does that even matter? Perhaps I should save the adrenaline for something more useful like Galrath Slash.
20AL is signifigant, and well worth taking for a 4A skill (if you've got space for it). That's 2/3 (very roughly) the damage you'd take without it. Check out Ensign's combat maths guide for more details.