There is such a thing as "educated guess". It comes from stuff like seeing the tooltips and doing the math and whatnot. There are things you need to play to know, and there are things you just need to hear about/see to know.
If you are told that the speed limit on part of the road you take to work every day gets reduced by 30%, with the only bonus of there being a new road nearing the end of that trip that have roughly the same length as the original one but splits the congestion, then you know that in the end you'll take more time to reach your work place without even going through it.
Majority of the summoners tools got reduced in effect. In return, they got Demi-Bahamut which you won't even be able to use in every other pull due to requirements to trigger it, some damage buffs that are not only not up permanently (duh!) but even when they ARE up don't make up for the losses (PS: Scholars pet cannot do anything when tethered, chances are that Summoners equivalent is the same) and a 15% chance of being able to cast buffed up ruin that still only reaches the current level of a spammable version (even if costly).
And no, the two dots total potencies are at 30sec operation, so even if they are "only" 40 behind total potencies of Bio, Bio II and Miasma currently, the potency lost is significantly higher, since in those 30sec, Bio II would tick three to four more times (120-160 potency more) and Miasma would tick one to two times more (35 or 70 potency lost), depending on whether the caster clips them or not. That's an additional 155 to whooping 230 potency lost on TOP of the 40 difference from total. Yep, that's why DoT-based DPS have it rough. They can't just cast their DoT whenever and say that they increased the damage output. The duration matters...
