These changes are going to be REALLY rough for solo scrappers.
I've seen a lot of commentary on the scrapper changes from a group PVE and PVP point of view, but basically none from a solo PVE point of view. Every post I've seen has totally glossed over the field portion of executing combos, either implicitly by not mentioning them at all, or even explicitly with statements like, "there will always be a field under whatever the group is fighting." This, however, completely ignores the additional challenges you'll see when you're responsible for your own fields AND finishers.
Sure, engineer has access to a lot of abilities that create fields, but they're all on longish (20+ sec) cooldowns, and now you have to line up those long cooldowns with the cooldowns of your blast finishers if you want to grant quickness. You're going to have to constantly micromanage your cooldowns to keep quickness up, which means you can't use your abilities based on the needs of the fight. So combat will turn from a fun, reactive encounter that rewards skillful use of the right ability at the right time to just mindlessly executing a rotation to keep up quickness.
Lots of our fields are stationary once cast. In a moving fight (e.g. any time you're fighting in the open world), this means you're going to have to choose between keeping up with the fight and waiting behind to execute finishers inside the fields. This is going to feel like absolute garbage to play, especially for a class that's so naturally mobile.
Some fields move with you, but that creates its own problems because you'll sometimes have to choose between using a finisher on an enemy at range, or using it at your feet to grant quickness (but wasting the ability's actual effect). For example, throwing a mine at the enemy for the damage and cc but not granting quickness, or just blowing it up at your feet, wasting the damage and cc but granting quickness.
Yes, the current system strongly encourages you to take and use certain utility abilities, but those abilities jive so well with the class's overall design and playstyle that those are the abilities you'd be taking anyway. After the changes, we'll theoretically (but not really) have more flexibility in what abilities we use, but we have to use them in a way that is counterproductive to the class's strengths and natural playstyle.