When you reapply your first DoT when it has 2s left on it, you don't miss out on the server tick and chance for a 150 potency attack that's off GCD for its recast timer to reset. By that time your first DoT is about to fall off and your second will soon follow. Clipping it earlier like around 5-6s just to reapply DoTs before buffs fall off is losing out on up-front DPS. Should you reapply as the DoTs actually fall off instead of just catching them before they do, you miss out on a server tick which is a loss of DPS. As for worrying about a difference of 10 potency, you are also forgetting the difference of 10TP. During battle, TP refreshes at 60 per tick. While Straight Shot does give a 10% critical hit rate buff, that is based on the specific stat rather than a flat 10% increase. On top of that frequently using a move that costs more than 60TP per GCD will eventually leave you TP-starved in longer fights should the management of the resource be an issue (there are BRDs who don't cross-class Invigorate or play a Battle Voiced Army's Paeon for 30-45s for a quick burst of TP regen. Heavy Shot has 10 more potency and costs 10TP less than Straight Shot, and has a 10% chance of proccing Straighter Shot which is a guaranteed crit worth the 70TP. The only time you should use Straight Shot outside of that is to reapply the buff. It all boils down to reliable and consistent DPS, which is never a DPS loss.

On a personal note, do not hesitate to go into detail. If you do not feel like delving into it, why bother posting when another person like myself doesn't mind explaining their case when asked? An exchange of information is never "clutter," and I seriously hope I'm not wasting my time on you if you actually think that way.