Actually DeNA or Mobage are by far the WORST of forcing you to p2p. Granted they are the biggest of mobile games, thier games you'll have to spend a couple hundred just to hope for a top 300 finish in events, the events last 5-7 days then a day or 2 later comes then next event. If you spend only 1k a month, then you'll only place around top 500 in each event.
This game is by far the most f2p friendly I have ever seen. Here you can get 80% of the characters for free with some grinding. Most games I've played you'll only get characters from packs, or event only characters that you have to finish around top 150 to get just 1.
That's why i feel people talking about this being p2w have no idea what an actually p2w game is.
Go play blood brothers, blood brothers 2, or star wars force collection, then come back here and tell me if this is p2w. Well actually you could. These games you literally have to pay hundreds to just not fall behind to much, and that's not even trying to compete.