We were working on our posts at the same time.
Good question: do you need more bullet? I'd say no. Here's my reasoning.
1) You ended up with a dead deer. No bullet failure there.
2) Yes, he ran, but you also took a less-than-optimal shot.
3) Stuff happens. Stuff happens inside deer that nobody can really explain.
The good news is that you got the deer. Your story points up the point I try to stress every year: be ready for a follow-up shot. You were. It might have been unnecessary, but it might have also saved you from losing the deer.
I have had a very few deer run in my career, but those that have usually have one thing in common: the shots were at a less-than-optimal angle. The shots were fatal, but there was not enough damage to cause immediate death.
I had one experience in 2005: shot a buck with my new 35 Whelen and the buck just stood there and looked at me. I shot him again. I shot him again. When it was all over I'd put 3 into his boiler room and left him standing. He finally fell over. I put my rifle on the rope in preparation to climb down from the stand when the buck woke up and started to get back on his feet. I had to pull the rifle back up quickly and reloaded. He expired while I was reloading.
Here's the rest of the story:
Hubert D. Buck Meets Mister Whelen
I did just like you're doing: I blamed the bullet. In fact, I switched from the Remington PSPCL (spire point) 200 grain to the SPCL(roundnose). I can't tell you if there was any difference in deer killing ability. Probably Hubert was just a fluke. I felt like I had to do something. In retrospect, what I should have done is wait to see if this happened on other deer before making the change. However, the new roundnose bullets worked just fine and I haven't changed since.
At the time, I theorized that the spire-pointed bullets were too tough and not expanding properly. This was actually in complete disregard to the reality of the situation; there was a good sized hole on the backside of the deer and plenty of damage to the internal organs. However, something had to be blamed, and the bullet seemed like the best target.
Once in a while you'll find this happening. Do not despair. It is probably not the bullet and probably not anything more than a cranked up buck who had a little extra vim left in him.