I can see things from both sides here, I've played the pet classes in other games aswell as Melee and I've had my share of things getting in my way be it other players or a pet that has some pathing issues. I think some of the concern here is not so much that the summon is on top of you but has positioned itself in front of your camera because of poor pathing or what have you.
Also keep in mind that if you make them taller you also have to make them wider, and while we have Roes running around they also aren't full of glowy particle effects. Some of these effects can be turned off mind you as I'm pretty sure I remember an option to turn off weapon/spell effects that were not my own. So even if you make them a bit taller like that you are still adding to the volume of them and I'd be willing to bet that some of them might end up being wider than a Roe and glowing.
Again it's not much different than having a player get in your way. Also as mentioned summoners only harness a sliver of the primal's power and from a lore point of view this may just be as much of that power as a summoner can handle without risk of losing control.
Also keep in mind that if you make them taller you also have to make them wider, and while we have Roes running around they also aren't full of glowy particle effects. Some of these effects can be turned off mind you as I'm pretty sure I remember an option to turn off weapon/spell effects that were not my own. So even if you make them a bit taller like that you are still adding to the volume of them and I'd be willing to bet that some of them might end up being wider than a Roe and glowing.
Again it's not much different than having a player get in your way. Also as mentioned summoners only harness a sliver of the primal's power and from a lore point of view this may just be as much of that power as a summoner can handle without risk of losing control.