Sorry for the "off topic", but...
Don´t forget the positive synergy Trolls as monsters would gain/add to their respective armies.
Well outweighs their new combination of drawbacks.
In my opinion, the BIG "5-cent" here is:
Trolls would 'less rarely' get left behind when composing a new list.
=> more Trolls on the battlefields

With 'less rarely' meaning:
Probably mostly because the reasons you point out, less defensive capability means enemy may actually engage them instead of total avoidance.
Thereby, under the course of several games, they will be picked more often when making/moderating a list.
Compare this with todays version, where they only are a command-sink-hole or/and a static flank-wall.
Woods, support, supported: there are several other units in each army for these tasks.
During charge would still be 6 attacks, 4+charge+monster. (compare 5+charge)