You definitely cannot attack another player's pet in Trammel unless you are in the same guild.
There are new options for attacking pets. I think you can damage pets/golems now in trammel when these settings are active.
If you are in Felucca, then the guild requirement is not in force.
Personally, at this point I just jewelry up and go hunting to raise melee/bushido skills. With appropriate jewelry range, gains are quick. I just craft/swap out jewelry.
I will start with brace/ring +15 each. I also craft a set that gives +10/+5 (one bracelet, one ring). Now as I gain skill, I adjust what I am wearing to stay in that sweet zone around my opponent's skill. This combo allows me to wear or not all skill ranges from +30, +25 (+15/+10), +20 (+15/+5), +15 (+15/none or +10/+5), +10 (+10/none) and +5 (none/+5). I have done this many times with taming to prove the gain method works well.
For melee and tactics you must be within +/-25 points of your opponent, although +/-20 is much better. It is noticeably slower at the extremes. This rule also applies to pets gaining wrestling and tactics.
Unless you are testing out the opponent with animal lore (110+

) it is hard to know your opponent's real melee/tactics. In a long training fight, your opponent will also gain skill against you. Sometimes it is handy to control skills via Discord on the opponent or your own pet.
Gaderian