Why I think the boss change was good
The main reason I think the change is good is that almost no one raided the Mons that were removed. Out of tier 1 and 2 only eggy was useful, but since it is already an easy raid for months everyone have good ones. For the shiny hunters they replaced karp with sableye.
They added 3 easily soloable tier 3 for rural players to get decent rewards, while keeping all the meta relevant Mons and not alienating the players who were working towards soloing them, also at least scyther is quite useful.
For tier 4 they added another meta relevant Mon while keeping the old ones. Then they replaced non relevant Mons with other non relevant Mons. Poliwrath should have been tier 3.
Answers
There's still a few players out there who are missing the final gen 1 starter evolutions (e.g. Charizard). Many players in my area were reluctant (or outright refused) to do these level 4 raids so finding enough people was difficult for them. At least now, those players can fulfill that goal themselves with the new level 1s, though not in one hit.
Similarly, I met a lady today who barely has any Scyther candy to her name and she was excited at the prospect of it now appearing as a raid boss.
I had raided Vaporeon a lot lately, but I have a 2954 and 2899 Raikou and a 2907 Zapdos, so why wouldn't I. Better than driving and waiting for a Suicune group. Think it is good to add and barely take away. However, if they didn't people in American cities would only do Machamp and Tyranitar this month. I got my 17th Tyranitar this morning, but guess I'll get distracted by a sparkling sableye/Porygon instead (actually no I won't). I'll mainly do ones that are convenient.
I don't know I would have liked to see a replacement instead of addition.
Now it is even more overpowered than it already was. And they could have made at least one of tier 3 bosses hard to solo. They are a joke.
Also they cut down the time to 45min but leave the egg 1h? It should have been the other way round
I posted this on another thread...so just a copy paste.
A few weeks ago, we had an event where we got massive amounts of bonus XP for evolving anything that was not already in our dex.
This would have given Niantic heaps of information about what people are lacking from their dex - it would be fair to assume that most people took advantage of as much XP as possible.
I believe they took that information, and gave us more raid bosses, based on what people are missing from their dex.
These aren't for the hard core...these are for those that are still playing that have holes in their dex.
The one thing I think they forgot to take into account is 'evo items' needed - but with that said the mons added that use evo items are also reasonably uncommon.
It wasn't a blind guess...it was based on verifiable data.
