GP is still good. You just have to go KR on hit build. I already understand the merits of Trundle, and he will be my fourth most played champ in ranked for S3. He was stronger earlier on, but the quality of him as a pick has gone further and further down. There are lots of reasons I don't think he's very strong right now. One of the biggest issues is that his ultimate doesn't signal the rest of his team well, so people don't realize the situations in which tanks can be focused down in fights. When you stack that on top of Trundle's inability to really make many plays on his own you run in to a difficult situation. Junglers don't really earn enough gold to open up his dive potential enough, and lacking hard engage or catch potential is rough. With popular champions right now heavy on wave clear his tower pushing rarely comes out, and with high mobility champs also on the rise there is little his pillar can do in many situations.
If you are running a Doran's Blade start Trundle isn't very reliant on blue buff as long as your masteries are set up right. Right now Trundle really just sucks for the meta. His damage output is too low and there aren't really good items for him to build that alleviate that. His tankiness doesn't really offset the fact that he lacks hard CC.
Still disagree on Gangplank currently being good. I admittedly tended to play him with heavy aggression from level 1 onwards when feasible (which used to be one of his key strengths) or as a lane bully in mid; with the latter back then you'd primarily run into squishy AP's with hardly any armor. Regardless, he can't really pull the above off anymore against competent players or strong overall picks and his alternative playstyle doesn't really jive with my own, never mind it being relatively time-consuming to reach his item threshold for the on-hit build (to my understanding).
RE: Trundle: I definitely agree with his ultimate being difficult to (visually) notice for anyone who isn't familiar with what he does, which regretably forces Trundle players to mass ping their target and inform their allies through chat on who they're likely to ult. Don't understand why they made it worse again with the rework, after their previous attempts to raise clarity. However, people usually listen to my persistent 'commandeering', so I've only run into a few instances where my ult ended up being a waste / missed opportunity on an otherwise sure-fire kill. His ability to make plays, or rather being able to set them up for others to take the glory, is more than fine. By the time you complete a big CDR item, you're already close to (if not entirely) maxing out your Pillar after Q for ridiculously short downtime and with today's current gungho mentality of leaning towards champions with high damage output or pick-off abilities, that's all you really need after a certain level of play (Gold I and up). Plus he earns enough gold for dive potential; his ult in conjunction with his favored items usually keeps him healthy enough if you select any half-decent target upon an enemy counter-engage (even with tower aggro), otherwise you tell your team to siege towers in between your obnoxious zoning. High mobility can be a problem, no questioning that, but right now it's very unlikely for draft pick captains to let Zed, Corki, Ahri, Kassadin, Fizz, et cetera slip through, never mind willingly leaving them open for the opposing team.
That said... On top of his less apparent Ultimate visuals, I
hate how clunky Trundle's auto-attacks feel post-rework (and prone to resetting much like unpatched Wukong), whereas his Q animation used to be easily cancelled without interrupting his chase momentum. Increased tenacity on his old W is also missed sometimes, but I'm not complaining until they severely nerf the sustain they replaced it with. Do wish you could ult monsters again though (albeit with a hard cap on health gains), since that used to allow you to sneak in an early dragon or baron. But I'm drifting off-topic here.
Damage-wise: I'd say that's a far bigger problem with the role itself rather than Trundle (and his is fine early to mid). Even Vi / Jarvan / Elise fall flat at being a good source of damage once late game rolls around and anything remotely similar to a carry style has been forcibly pushed out by Riot. Relevant items or champions for this style promptly got their offensive advantages nerfed (sometimes undeserved or even due to the ADC's), there simply isn't enough gold or experience in the jungle itself and all that's left are the defensive items that got their durability or gold efficiency reduced. Sure, the aforementioned champions are better at hard-engaging, but the reason why they draw as much attention as they do (on the receiving end) isn't because they're likely to kill a high-priority target at that point in time by themselves. Exceptions are of course when you're snowballing like crazy or if the match in general ends up being a stomp, but you can make any champion look better under those 'ideal' circumstances (which again, are far less likely to occur against decent players). Point of the matter being though; most junglers are currently shoe-horned (out of necessity) into being a tanky pseudo-support with the possibility to engage,
and they need to be able to fight back / survive on their own early on as well (thus Nautilus et al falling out of favor). Which... in turn Trundle does with far less risk involved, while able to punish high-risk high-reward all-ins and while being able to protect his carries.
Of course there's always those Lee Sins that end up as a force to be reckoned with from beginning to end, but he requires a much higher level of mastery to pull that off consistently (which I don't view as a champion limitation, mind you). Even if you don't agree with my views on Trundle, jungling in Season 3 has gotten incredibly stagnant for everyone involved at a certain level and for that reason I'm looking forward to what Riot has up their sleeves for the upcoming pre-season.