I tried this out in part of Pits of Isengard as well as some skirmishes the other day and overall there is only 4 things I would like changed about the line.
1) Induction times of Bard's Arrow and Distracting Shot are much too high. If traited 5 deep with the capstone could these be lowered to say .5s? Only reason I say this is adapting to resists is very difficult with the induction being the way it is as the mob is usually in melee range of their aggro target by the time you see the resist, hit the skill and the skill lands on the target. When everything is going to plan its fine and you can keep 2 mobs locked down with relative ease (one with traps, the other with dazes) but that one problem keeps it from being a truly reliable CC role.
2) Traps resist far more often than any other form of CC. While in the Pits I was using Set Trap, Distracting Shot, and Bards Arrow. I noticed that there were one or two resists with my Distracting Shot over the course of the run, but at least 6 or 7 resists with Traps. Not sure it it was just bad luck for that day but it just seemed like traps were much more unreliable.
3) Give a defensive debuff to the line. For instance the capstone could give Heart Seeker a 10% outgoing damage debuff for one minute. As an alternative allow Blood Arrow to have a 20% chance to place the 10% outgoing damage debuff for one minute. The main reason for this is everyone rightfully scoffs at the -900 BPE penetrating shot debuff because the Hunter's DPS loss (between 500-800) and DPS increase to the group (at most ~9%) basically cancel each other out. If you have 8 people DPSing at say an average of 1000 DPS each of them gains ~90 DPS for a total of 720 DPS increase to the group as a whole, which is right about in range of what is lost by the hunter.
Overall I think these changes of a short induction on CC, reliable traps, and a defensive debuff would make the Trapper of Foe hunter much more useful.
(Also Spring loaded traps currently allows for Set Trap to be used in combat making the combat trap trait totally useless)
(Also the Sturdy Traps trait causes the incoming damage debuff from the Spring Loaded Traps trait to not occur)