Spiders sometimes do not attack when they should

Tested in Windows 10, version 1.4.2.0.

I was able to come right up next to a spider that was not looking in my direction, and it didn't attack me. However, any spider that happened to turn toward me attacked spontaneously.

In the nether, I encountered a blaze in a covered corridor that didn't launch a fireball attack at first. It seemed to try to rise and its warning flame animation ran, but it immediately descended again. In fact, it came closer as I waited and when it finally reached me, I took damage (I don't know whether this was a melee attack or just fire damage). I backed up gradually and it followed me. After about 90 seconds it finally launched a fireball attack at me. I also explored and found many blazes in more open areas. All that were within 15 blocks or so spontaneously launched fireball attacks, mostly after a 5-10 second delay. A few appeared not to see me; they were at long range, but still close enough for me to shoot with a Power IV bow. This seems close enough that they would have attacked if I were playing Java Edition.

Also in the nether, I encountered a few ghasts. They also spontaneously attacked once they turned toward me. Their behavior seemed consistent with my past observations of ghasts.

I will call this partially confirmed, although I'm not sure it was ever the case that spiders, blazes, or ghasts that weren't looking toward you would see you right away and attack. The only mobs I'd be confident saying that about are zombies, and endermen you're looking at. So this could be working as intended.

I've only really noticed this with blazes. Other hostile mobs turn and come after me the instant they detect me, but blazes just float there and look at me while I walk right past them. The only time I've taken damage was when one came out of a side passage and floated into me, dealing contact damage. But I haven't been fireballed by them literally for months. At times when I should be getting absolutely pelted by blaze fire there's not a single hiccup from them. It's weird. Like dealing with noisier, smokier cows and sheep. Not neutral like spiders, how they ignore you during the day unless you hit them first, but completely passive.

I can confirm the behavior of the ghasts. They're supposed to attack me from up to 100 blocks (very long distance). This happened on 1.5.0.10. But when I approach them (about 32 blocks), they turned and attack me continuously

Still affects 1.6.0.6

Happened to me with a baby drowned on 1.5 Win10 edition.
After about 60 seconds of dancing around him, he started attacking me.

Still affects 1.6.0.8

Yeah, ghasts only shoot when they get quite close. A lot closer than what I'm used to in java. And blazes are hardly ever hostile (so the nether is less stressful, I guess). I have a long time to kill a blaze before it notices me. 

On 1.11.4 and 1.12 betas ghasts now attack me correctly when they notice me but is still an issue with blazes and spiders

affects 1.13.0.1

affects 1.13.0.2

Is this still an issue in the latest version?

Still an issue for spiders and blazes in 1.16.40, but I'm in favour of tracking them as different bugs: MCPE-93769 (spiders) and MCPE-73279 (blazes) because they don't seem to be the same "neutrality" issue.

I believe this issue is working as intended because it appears to be deliberately coded. In the vanilla entities\spider.json the "minecraft:behavior.nearest_attackable_target" component includes the line

"attack_interval": 5,

This parameter makes spiders wait for a random interval between 0 and 5 seconds each time they attempt to find a target.

You can see the impact of this parameter in the following videos. Large groups of spiders and husks are held behind a barrier in daylight. Pressing a button removes the barrier and sets the time to night. The husks all attack immediately. The spiders attack in greater numbers over time.