Players will never create a solely condition damage focused offensive (glass) build focused around these skills: Flurry and Flaming Flurry (Warrior), Torch weapon skills (Guardian), Sneak Attack, Malicious Sneak Attack, and Repeater (thief), Confusing Images* (mesmer).
The reason players won't use these competitively is that the user is vulnerable while attacking, and the opponent isn't really being killed while the skill is being channeled. Resistance is also a big contributor to the ineffectiveness of these builds. Players on the receiving end will just eat the attack while killing you (since you pretty indisposed while attacking), only to pop resistance or cleanse after you are dead or running away (if even necessary). The reason other channeled skills like Rapidfire (Ranger), or Unload (Thief) are actually useful is that the player on the receiving end is having their health drop significantly AS THE SKILL IS CHANNELED. This means that the skill itself is somewhat defensive since it puts the enemy immediately on the defensive. There are two other reasons I believe these builds haven't seen the light of day since the early years of GW2: The over-abundance of Reflections/Projectile blocking, and the lack of amulets which support a sustaining condi pressure builds (ex: Max Heal Power and Condi Dmg, Min Expertise, and Vitality). There are other reasons these are not viable I'm sure.
*Confusing Images is only strong in the meta recently because of it capacity for major Power damage, coupled with the fact that it's a ranged beam attack (not projectile), on a weapon which has a built-in block. Also the mesmer can do a lot of defensive things while channeling.