You seem to predicating your entire suggestion on this premise, but, quite frankly, it's a false premise.
Taking out the healer first is most certainly NOT the only viable strategy. It may not even be the best strategy, depending on the circumstances. That is actually the main difference between Feast and WD. In WD, the kill order literally was fixed. You always killed the healer first. It was the only way to win. In Feast, it is not. The buff boxes at the start of the match make a huge difference in which target can, and should, make the priority. It's not always the healer, especially if they have the defense buff. In fact, more often then not, the priority target is the melee dps, because they stand to pose the biggest threat at the start of the match. Even if you do go for the healer at the start and score a kill, the priority immediately shifts. The entire concept of heavy medal stacks and available coins encourages you to chase other targets, because the dmg on those targets is higher and the reward is greater. The only time that purely prioritizing the healer is a viable strategy is if that healer is so good that they are carrying their team, and even then, that's only the case if the dps are too weak to score kills. Otherwise, thinking that killing the healer first is the best and universal kill order is a novice mistake that can actually cause far more harm than good, especially if the healer is good enough to carry themselves through a burst or CC.
The reason I mention the healer's personal skill is because healer's do, in fact, have the resourced to heal through a double burst. It's not easy, certainly, but it is possible. For one, they have an awful lot of emergency heal measures that they can take advantage of if they need to (such as big heals like Benediction, or PvP skills like Attunement, etc). The strongest healers I've seen in the Feast actually needed to be CC'd, otherwise nothing would ever die. That's how potent their heals can be, if used correctly. It's not uncommon, especially in mid-ranked matches, to see an LB fail to kill a target, or have a match get thrown into Culling Time. It all depends on how skilled the healer is at using the tools they have available to them. The problem isn't with those tools. They're strong enough. The problem is with the healer's ability to manage their healing while also dodging the CC attempts of their enemy. A lot of healers lack that skill, and a lot more tank/dps teams fail to give adequate support to their healers when they need it (such as with purifies, covers, stuns, etc). Reducing the number of dps in the match is not going to fix that problem. It would make CC easier to achieve, but most dps can't capitalize on that time with two people bursting, let alone one. The dramatically reduced dps would make it far easier for healers to breeze through the average dps burst. To be honest, I wouldn't be surprised to see Culling Time become a lot more common as a result.