This answer is going to be over the top, so I apologize in advance, but I have had a decent amount of success playing Troggzor. Here are my thoughts.
He is most effective if used in a taunt deck. As /u/LimeyLassen stated, if you can play him behind a taunt minion, this forces the opponent to attack through the taunt to get to Troggzor. If you can continue to drop taunt minions, and go face with Troggzor, the game is over.
The tricky part is knowing when to drop him. If you do a search on this subreddit, you will find a lot of people that say that you can only play him on an empty board, or when you are ahead. This is not entirely true. The important thing to consider is HOW MUCH DAMAGE IS ON BOARD. If Troggzor cannot be killed the next turn by what the opponent has on board, you drop him. The opponent will be very hard pressed to kill Troggzor the next turn without triggering his power.
Another common misconception is that his power lies in him spawning other Trogg's. This is not the case. His power lies in the opponent PLAYING AROUND him. This is where playing behind taunts comes in. If Troggzor can stay on board, the opponent is continually forced to make subpar plays, without using spells. This advantage quickly snowballs and can lead to easy victory.
However, there are still spells that Troggzor is vulnerable to. Priests can cast Shadow Word Death then Shadow Word Pain on the Trogg it spawns. Warrior can do any combination of execute/shield slam. Shaman has Hex, Mage Has Fireball and Rogue has Blade Flury. It may seem counter intuitive to use a spell to kill Troggzor, but again, his value comes from being on board, not actually spawning Trogg's.
Troggzor is also vulnerable to silence. While this is arguably the best way to deal with him, it still leaves a 6/6 body on the board. Also, not every deck runs silence. In fact, if you play Troggzor a lot, you will find that he rarely gets silenced at all.
A few other notes:
When I say taunt deck, I really mean Druid taunt deck. The dream play is a turn 10 Troggzor+Innervate+Druid of the Claw/Sludge Belcher. Also, playing him on curve is ill advised. As a druid, I rarely have any semblance of board control by turn 7 unless I drew a dream start. The turn 10 play is often better, or waiting even longer for your opponent to run out of steam and not have an effective answer.
And to answer your question, no, Troggzor will not replace Dr. Boom. Troggzor is arguably more effective, but only under the right conditions. Dr. Boom is good no matter when you play him.
TLDR: Troggzor is a game winner if played correctly, but will never be Dr. Boom.