Purely personal opinion here. Seems more like one of those personal choices this game is filled with.
I've been satisfied with a lvl 3 ToR in my experimental city for 2.5 years. Never bothered leveling it up, just left it there. Someone pushed it up to 4 last week.
Sure, Goods and FP Relics are sweet and all, but heck, I was debating tearing it down a while back. Then INNO dropped the AD, so I keep it around for more AD fodder.
Lvl 2 ToR in my newest (9 months) city. I'm in no hurry to level that either.
A couplle years back an apprentice told me he wanted to put a lot of effort into leveling ToR. We talked it over, seems that of all the Rewards he was most interested in the FP and Goods. We did the math, and when he looked at the cost of of increasing the ToR levels versus the increased chances of the FP and Goods Rewards he decided there were a lot better things to do with the FPs.
Note, I'm not saying that lvling a ToR is a bad thing, seems like a fine idea, just maybe not the best use for FPs at some points in the game.
I won't try to convince anyone else that a low level ToR is a fine addition to a city. Or that leveling up a ToR may not be the best option available.
Seems as useless as debating issues like HS and city defense structures and Victory Towers. Folk are gonna disagree, too many subjective factors.